Laser cutting is based on various simultaneous sub-processes. Firstly, the focused laser beam provides the required energy to heat and melt the material. Secondly, the cutting gas flow accelerates the melt and removes the material out of the kerf. In addition, the melt flow and local phase transitions play an important role in the redistribution of energy within the process zone. The cut itself and the achievable process performance and quality are the result of the complex interaction of the sub-processes. Due to the momentum and heat transfer between the gas and the material, the gas flow has a decisive influence on cut quality and the formation of burr. Furthermore, the differences in quality for CO2 and solid-state laser cutting is linked to the influence of a changed gas flow due to wavelength dependent absorption effects.

This study experimentally evaluates dynamic beam shaping in beam propagation direction for cutting 20 mm thick stainless steel, with a focus on improving cut quality and reducing burr and surface roughness. Both 20 kW cw and 15 kW pw laser cutting tests were carried out for the first time. By using a novel tool to model the laser spot dynamics resulting from rapid focusing and defocusing, we achieved significant improvements in cutting performance. This tool also enabled the inclusion of cutting speed, nozzle geometry, cut contours and beam overlapping, providing a comprehensive understanding of the interaction between the laser beam and the workpiece. Our results demonstrate a reduction in burr formation and a decrease in the roughness of the cut edge, manifesting and highlighting the potential of dynamic beam shaping for enhanced laser cutting of thick stainless steel.

Burr formation in laser cutting reduces the quality of the cut and increases the need for extra processing of parts. In this paper in-situ high-speed imaging has been used to gain insights into the impact of the melt dynamics in the cutting kerf on the formation of burr during laser cutting of metal. The images captured both, the melt dynamics in the kerf and the adhesion of the melt to the lower edge of the sheet. The results show that the formation of burr is due to the detachment of melt droplets from the cutting front to the flanks of the cutting kerf, which then adhere to the rear side of the sheet. In addition, the adhesion of molten material at the rear side of the cutting front and the subsequent flow of the molten material along the lower edges of the cutting kerf also leads to formation of burr.

Latest research on laser cutting has revealed significant improvements in process productivity and cut quality through the applications of dynamic beam shaping techniques. The present work aims to study the effect of axial beam oscillations (along Z-axis) on laser fusion cutting process through analytical modelling and experimental investigations. While existing literature has primarily focused on dynamic beam shaping employing harmonic oscillations, this study explores the impact of various oscillation waveforms, including sinusoidal, triangular, square, ramp-up, and ramp-down patterns. Initially, an analytical model was developed to evaluate the laser power distribution within the process zone for different oscillation patterns. Furthermore, the effect of axial oscillations, superimposed on the cutting direction, was experimentally investigated using 20 mm thick AISI304 stainless steel. Experimental results demonstrate notable improvements in process performance through axial oscillation, either by reducing burr defects at the same processing speed or by increasing productivity while maintaining equivalent part quality.

Gigacasting facilitates the production of large, complex parts in a single process, reducing costs and increasing efficiency. After casting, laser cutting ensures a flexible postprocessing for precise contours, as well as removal of overflows and runners. High-Power Laser cutting of aluminum based gigacasted components with a thickness of up to 30 mm provides high quality production.

High-performance lasers, typically starting from 3 kW, are required for efficiently cutting thick aluminum. Maintaining a high working distance during the cutting process is essential, as it allows a three-dimensional accessibility of complex geometries. The laser beam melts the material, while assist gases like oxygen influences cutting quality.

This development of laser cutting for postprocessing gigacasting components enables lightweight, durable automotive components with complex geometries while reducing material waste. By combining these technologies, the production of future mobility parts is revolutionized, resulting in carbon reduction and better cost-efficiency for the product lifecycle.

Optical imaging of internal organs is a crucial tool for advanced medical imaging applications, particularly for minimally invasive procedures like bronchoscopy. Currently, the shape and size of the lens systems are restricted by manufacturing limitations. Incorporating imaging optics at the end of a coherent fibre bundle (diameter 350 µm) offers the potential for far-field imaging of the distal lung reducing the overall catheter size to ~1.8 mm. This enhancement would facilitate real-time 3D reconstruction for spatial airway mapping during navigation. A femtosecond direct laser writing system is incorporated to fabricate micro-lenses with high optical quality. To ensure robustness and reusability, these microlenses will be directly printed onto a fused silica end cap, manufactured using ultrafast laser-assisted etching (ULAE). This talk presents an overview of the methods used to fabricate a functional imaging system to be incorporated with a novel bronchoscope, addressing the challenges and innovations involved in its development.

Two-photon Polymerization (2PP) is probably the technique which offers more degrees of freedom for the fabrication of complex 3D structures with submicrometric resolutions. However, it is known that the main drawback of 2PP is the reduced throughput. Several optical approaches can be used to overcome such issue, like the use of Diffractive Optical Elements, Interference optical setups, or Spatial Light Modulators (SLMs); being SLMs the only elements that allow increasing the productivity of 2PP, since the use of DOEs and Interference setups is limited to the fabrication of periodic structures

The work presented here shows our latest results for the fabrication of 3D features with lateral sizes well below the micron range using a combined phase-amplitude laser beam modulation of the laser beam. The combination of optimized scanning strategies with the modification of the laser optical wavefront shape will be presented as a feasible alternative for high throughput 2PP.

In this work we present our recent results on multi-photon polymerization (MPP) using mode-locked diode lasers. While conventional MPP systems use titanium:sapphire lasers or fiber lasers, our goal is to replace these laser types with monolithically mode-locked diode lasers. Since diode lasers are much more compact, cost effective and allow for direct modulation without the need for additional components such as AOMs this will allow us to build a compact and cost effective MPP system. The diode laser used for this work emits mode-locked laser pulses at 780 nm at a pulse repetition rate of 6.6 GHz, an average power >1.5 W, and pulse length > 3 ps. We will demonstrate how to operate the laser, find the best point of operation for 2PP and present printed structures and an analysis of the writing process using these laser sources.

We present an innovative approach to holographic layer-by-layer 3D printing by adding temporally and spacially shaped femtosecond pulses elements to the overall design. 2D printed patterns are generated using a Digital Micromirror Device (DMD), which also at the same time spreads the spectrum of the visible (515 nm) fiber laser used. Projecting these patterns with a 4-f system gives reduced intensity temporally while at the print plane simultaneously bringing the spacial and temporal elements to a focus. This approach mitigates proximity effects and out-of-plane hot spots. Previous limitations of low laser repetition rates and off-times between layers, where overcome with a high-power fs fiber laser operating at 500kHz in combination with an external pulse compressor and frequency doubling system.

Laser welding is a precise material-joining technique offering localised heating, minimal thermal damage, and contactless processing. For transparent polymers without an absorber layer, ultrafast pulses can trigger the non-linear phenomena needed for welding. This study optimises the scanning speed and fluence per pulse for welding polycarbonate using a 1.03 μm wavelength femtosecond laser. The cumulative fluence was calculated at the weld seam's centre and edge to determine the maximum and minimum energy per unit area, and the weld seam quality was assessed optically. Optimal results were achieved at scanning speeds of 10 and 20 mm/s with fluence per pulse of 0.38 – 0.72 J/cm2 and 0.65 – 1.14 J/cm2, respectively. Two damage regimes were identified: one caused by high cumulative fluence (283.4 J/cm2) at low speeds (5 mm/s), and the other by high fluence per pulse (1.50 J/cm2) at high speeds (30 mm/s). These findings provide insights into parameter selection for welding transparent polycarbonates.

Laser-based manufacturing enhances fiber bundle (FB) performance for biomedical imaging. FBs, widely used in endoscopy, suffer from pixelation, limited 2D imaging, and low photon efficiency. To address these challenges, we demonstrate a laser-based approach to improve FB functionality.

First, CO₂ laser-induced thermal expansion of fiber cores enhances photon efficiency without significant crosstalk. Second, femtosecond laser ablation and two-photon polymerization create holographic structures on the fiber facet, enabling dispersion correction. This transforms the FB into an ultrathin, flexible diffractive lens with a 500 µm focal distance, optimized for microendoscopy.

With a total diameter of 400 µm, the fiber lens integrates easily into raster scanning and wide-field microscopes, enabling unpixellated fluorescence imaging with 1 µm resolution. This advancement enables easy-to-use, low-cost, minimally invasive optical tools for diagnostics and research.

This paper presents an extension to a general-purpose hydrodynamic simulation model for laser-based processes, enabling the simulation of ultrashort pulse laser ablation of dielectric materials. The model incorporates free electron generation through multi-photon and tunneling ionization, avalanche ionization, charge carrier recombination, as well as their diffusion and advection. These processes are fully coupled with compressible multi-phase hydrodynamic equations, allowing for the investigation of phenomena typically unobservable experimentally.\\

A comprehensive validation against experimental data assesses the model's accuracy across various laser parameters. The study also includes a detailed parameter analysis, providing insights into optimal processing conditions. Additionally, the effects of novel beam shapes on ablation dynamics and material removal efficiency are explored, such as the employment of Laguerre-Gaussian beams with orbital angular momentum, so called vortex beams. This extended model offers a powerful tool for understanding and optimizing ultrashort pulse laser ablation of dielectric materials.

Ultra-short pulsed (USP) laser ablation of metals is a key process in precision manufacturing, enabling applications such as micro-drilling. Advancing both its fundamental understanding and industrial applicability requires a detailed investigation of the underlying ablation mechanisms.

This work presents results of a fully three-dimensional multiphysical simulation framework based on continuum mechanics, incorporating a two-temperature model, Drude absorption, compressible Navier-Stokes equations, and pressure- and temperature-based phase change models. To enhance predictive power, a pseudo van der Waals equation of state for the gas phase and a novel material model for the liquid phase have been implemented, specifically designed to address near-critical and supercritical regimes.

The study elucidates ablation mechanisms, from spallation to phase explosion, across a wide range of fluences governed by variations in pulse energy, diameter, and duration. The findings provide new insights into USP laser-metal interactions, contributing to both improved process understanding and optimized laser processing strategies.

The package Macromax treats the solution of Maxwell's equations as a scattering network and enables high acceleration of wave calculations through GPU acceleration. It has been extended to allow the simulation of 2D laser ablation with high resolution in the nanometer range for rectangular grids with sizes from thousands to tens of thousands of square micrometers.

This approach allows the laser drilling process to be studied in detail, including the absorption mechanisms of capillaries, incubation and the side-channel phenomenon. The numerical results are analyzed and compared with experimental findings.

In semiconductor manufacturing, achieving smooth, defect-free surfaces on silicon wafers is critical for advanced electronic and photonic devices. Laser polishing offers a promising solution, yet controlling heat transfer to prevent microcracks, excessive heat-affected zones (HAZ), and surface defects remains a major challenge. In this research, numerical simulations are used to investigate the influence of laser parameters including laser power, frequency, and scanning speed on temperature distribution, melt pool depth, and final surface integrity. The results highlight the necessity of carefully optimizing these parameters to control thermal gradient, minimize HAZ formation, reduce roughness, and preserve wafer integrity. By systematically tuning process parameters within narrow operational ranges, the simulation framework provides a robust predictive tool for defect-free laser polishing on silicon substrates. This work paves the way for more efficient, high-precision polishing processes in the semiconductor industry, ultimately contributing to the reliable and cost-effective production of next-generation devices.

Beam shaping is essential for optimizing femtosecond laser micro-processing, especially as higher laser powers, including kilowatt-class systems, become available. However, identifying the ideal beam shape for each application remains challenging.

In this work, we present a numerical simulation model designed to efficiently predict the impact of various beam shapes on femtosecond laser processing. The approach is based on the Two-Temperature Model (TTM), allowing for rapid simulations of energy absorption and heat dissipation dynamics. We will detail the computational methods used, the model validation process, and its predictive capabilities.

The study explores the effect of specific beam shapes on different materials, demonstrating how optimized profiles can enhance precision in machining, reduce tapering, and improve ablation efficiency. Simulated performance metrics will be compared against conventional Gaussian beam processing to highlight the advantages of advanced beam shaping strategies.

An essential basis for reliable and targeted process control is understanding the interaction between the laser beam and the material being processed. The use of low-coherence interferometry (OCT) as a sensor technology for laser microprocesses is an example of the possible applications for obtaining in-situ processing results.

Since most applications with short or ultrashort pulsed lasers are a combination with scanning technology to deflect the laser beam, the sensor must be adapted to these specific processing heads. This contribution deals with applications where it is necessary to measure the ablation depth in-situ in order to control the process. With a high measurement frequency of the sensor device, it is possible to achieve this goal if the wavelength of the light source is carefully chosen to reduce the chromatic shift induced by the F-theta lens in the scanner device.

Laser powder bed fusion (LPBF) is a digital manufacturing technology that enables the production of components with unparalleled design freedom and complex geometry from digital designs. LPBF has ubiquitous product applications across different industries, including aerospace, biomedical, energy, marine, and robotic. However, it remains challenging to qualify the process and products of LPBF due to the complex laser-material interactions and unpredictable nature of the process dynamics that occur on the microsecond and micrometre scales. In this seminar, I will present the latest work from my research group on these interactions and process dynamics in LPBF. Our group uses synchrotron X-rays combined with a Quad-laser in situ and operando metal 3D printer, and digital twin models to reveal, quantify, and explain these process dynamics during LPBF. The insights gained from our research are transforming our fundamental understanding of LPBF across various materials, contributing towards process and product qualification.

Electric mobility is posing new challenges to laser technologies, increasingly adopted as flexible and digitally integrated tools. The wide availability of laser sources, and beam shaping solutions makes selecting the most suitable configuration complex. This contribution highlights the need for a new metric to define beam shaping solutions, considering the three laser beam dimensions: space, time, and wavelength. Recent application cases are presented, including hairpin welding, zinc electrode via L-PBF, and lithium battery processing. These examples show the importance of selecting the beam shaping strategy and process parameters, which are increasing due to the rising number of variables. A 3D model of hairpin welding demonstrates how simulation supports optimal condition identification alongside experimentation. The talk concludes by discussing how sensing and monitoring, enriched by the dimensions introduced by beam shaping, support process understanding and detection of shifts from stable operation.

Previously laser cutting by facture propagation technique has been successfully used in thin glass cutting. In this talk we present use of the technique in cutting of ultra-thin ribbon ceramics. Unlike thin glass, the cutting process is self-initiating due to the presence of grain boundaries in the material. As an example, we used a CO2 laser beam with Gaussian intensity profile to cut zirconia ribbon ceramics with a thickness of about 40 um. Under optimized conditions, the cut cross-section showed no evidence of damage or crystal grain growth. The cutting speed scales with laser power, ranging from tens of millimeters per second to meters per second. We also examined the strength distribution of the cut edge, observing a minimum strength of over 900 MPa. This technique has been similarly applied to ultra-thin ceramics of other compositions, yielding equally excellent performance.

Lasers are an excellent source of directed energy. In this study, we developed a novel cutting method for rein-forced concrete (RC), enabling separation of brittle RC vitrified by ultra-high-power laser ranging from 30 to 60 kW in power. The input laser energy, ranging from 13 to 124 MJ, was initially used to cut RC of 0.5 or 1 m in length without assist gas. Instead of the assist gas, the molten concrete was pulled down by gravity. Vitrification of the RC occurred under all conditions. A 50-kW laser with an energy of 43 MJ successfully penetrated 1-m RC by elevating the laser with focal reciprocation along the optical axis at a travel speed of 6 mm/min. This study validates the potential outdoor application of ultra-high-power lasers, including cutting during the decommissioning of nuclear power plants.

Carbon fibre reinforced plastics (CFRP) are widely used in lightweight applications. The global lack of production capacity for carbon fibres (CF) leads to high production costs. Therefore, semi-finished CF products are expensive. There is also a low resource efficiency that is driven by left-overs from the semi-finished products in CFRP part production.

A laser cutting process for endless-fibre-reinforced semi-finished product left-overs to produce CF-chips was developed. Chips can be used as a basic component for valuable, long-fibre composite parts instead of shredding them for filler material in concrete or incinerate them with energy recovery.

In this investigation, laser factor settings were varied to machine chips of 10, 15, and 20mm edge length. These were used to produce long-fibre reinforced laminates that were cut into coupons and evaluated for mechanical strength.

First results indicate tensile strengths between 75 – 400MPa depending on fibre length of the chips.

Laser cutting of flax fiber reinforced composite (FFRC) is a promising technology as it can avoid typical defects of mechanical cutting like fraying or delamination. However, when cutting with wavelengths in the NIR the high transparency of the matrix coupled with the good absorption of the flax fibers causes an inhomogeneous energy deposition.

To increase the absorbance of the matrix thermoplastic samples and FFRC samples with natural and synthetic absorptive additives were produced . The absorption coefficients at 1064 nm and 532 nm of the modified thermoplastics were measured using a reflectometric setup. Subsequently, the 2 mm thick FFRC samples were cut with a Yb:YAG laser at velocities between 2 – 8 m/min and power levels from 250 – 2000 W. The measured absorption coefficients correlate with the required cutting power, resulting in a power reduction of up to 45% compared to unmodified FFRC.

Advanced materials, like ceramic matrix composites (CMCs) which exhibit superior thermomechanical properties are crucial for addressing 21st century engineering challenges. However, these materials have low machinability and are a challenge to process with state-of-the-art laser or mechanical methods. This study investigates the characteristics of hybrid (sequential) laser-mechanical machining (HLMM) of 6 mm thick alumina oxide (Ox-Ox) based CMC. HLMM involves bulk material removal using high-power continuous wave laser followed by mechanical finishing. Comparisons are made with standalone laser cutting and mechanical machining to assess HLMM's performance in terms of quality, productivity, and future technological progress. Results show a 70% reduction in cutting force and significant increase in productivity compared to standalone mechanical tool cutting; and 74% improvement in surface roughness and full elimination of thermal defects from the material's cut edge compared to standalone laser cutting. HLMM exhibits an overall cutting speed of 560mm/min for 6mm thick Ox-Ox CMC.

In continuous glass manufacturing processes, such as fusion draw, it is essential to cut a glass ribbon into sheets without disruption of the glass flow. This is typically achieved through the use of mechanical or laser cutting apparatuses, which enable the separation process by cross-ribbon scoring followed by bend breaking. This study presents a method for on-draw cutting of hot glass ribbon through localized melting using an infra-red laser beam. Our findings demonstrate that cutting the ribbon, which is already formed but maintains temperature within the annealing range, allows full body ribbon separation through glass melting without generating excessive residual stress. Additionally, this laser-induced process results in the formation of a rounded edge, which might eliminate the need for further finishing in certain applications. An experimental platform, comprising the glass draw, and laser system developed along with a theoretical model of the process are presented.

Laser powder bed fusion (PBF-LB/M) enables the production of lightweight, customizable titanium components, but the minimum feature size is limited to several hundred micrometers.

This work demonstrates the use of ultrafast laser percussion drilling (260 fs) to overcome this limitation by fabricating precise shallow dimples and deep microholes in PBF-LB/M-generated Ti64 parts.

Dimples as small as 50 µm with laser-induced periodic surface structures (LIPSS, ~1 µm spatial period) were obtained, highlighting enhanced microstructuring capabilities. The study shows that peak fluence and pulse number are key to controlling dimple geometry, while pulse energy determines the depth progression and achievable depth of microholes. Through-holes of 1.5 mm depth and 110 µm diameter were achieved, corresponding to an aspect ratio of 13.5.

These findings demonstrate the feasibility of using ultrafast laser drilling to introduce micrometer features and high-aspect-ratio geometries, broadening the applications of PBF-LB/M components in high-precision fields.

Advanced high-speed synchrotron X-ray imaging techniques enable real-time observation of the ablation of micro-holes and -grooves in stainless steel using ultrafast lasers. The images reveal valuable insights into the underlying dynamics of the processes.

Recent findings highlight the role of heat accumulation and laser polarization in the formation of micro-holes. Two mechanisms driving the side channel formation were identified. The first involves lateral deflection of the borehole tip, while the second occurs when drilling resumes after an interruption.

During multi-scan ablation of grooves, heat accumulation causes melt fluctuations and the formation of numerous micro-holes at the groove bottom, which significantly influences the depth progress.

These observations improve the understanding of transient effects in ultrafast laser processing, enabling the development of optimized laser parameters for improved precision, fewer defects, and enhanced productivity in industrial applications.

Conventionally, metals and plastics compete due to their differing mechanical, physical, chemical, and tribological properties. However, hybrid components that synergistically utilize the advantages of both materials present significant potential for weight reduction, functional integration, and cost savings. The production of plastic/metal hybrid components can be efficiently achieved during the primary forming process of the plastic part (injection molding) using macrostructures, eliminating the need for additional joining technologies. Macro structuring on metal components is accomplished through laser or electron radiation via repeated micro-welds (Surfi-Sculpt®). The strength of these structures can be tailored by adjusting process parameters, orientation, and geometry of the micro-welds. This study presents initial results regarding individual structural strength on stainless steel samples. It demonstrates the dependency of bending strength and structure geometry on ambient pressure as well as the increase in structural strength in welding direction. Higher energy input allows for elevated macrostructures but may reduce bending strength.

In pulsed laser ablation, the interaction of successive pulses is significantly affected by the surface morphology generated by preceding pulses. This study investigates the impact of burr formation around laser ablation spots on the absorption characteristics of subsequent pulses, highlighting its critical role in determining the sidewall quality during laser percussion drilling of metals. The findings allow for new approaches in optimizing laser parameters for enhanced machining precision and surface quality.

Ultrashort pulsed (USP) lasers have been widely investigated in micromachining of various materials. The unique laser characteristics induce nonlinear material absorption mechanisms and result in excellent processing quality. However, conventional USP laser processes are typically confined to 2-2.5D due to limitations inherent to conventional laser machine concept.

We introduce an ultrashort pulsed laser robot (USPLR) system, wherein a USP laser is attached to a robot axis, beam guidance is realized by intelligent, adaptive discrete optics. The combined movement of the robot and a 2D galvanometer scanner not only enhances the processing flexibility in one plane but also extends processing capabilities to three dimensions. Here, we present and discuss comprehensive experimental results on the performance of the USPLR system and demonstrate first applications in material processing. In addition, we compare an alternative beam guiding concept for the USPLR system based on an optical fiber.

Lithium metal as an anode in the solid-state battery is a promising alternative to the intercalation type of anode in the lithium-ion battery. However, cutting of this component mechanically is challenging due to its high surface adhesion, chemical reactivity, and low rigidity. On the other hand, the melting temperature of this material is very low (180 °C) compared to conventional metals, rendering it problematic a stable thermal cutting operation. While the laser is an appealing solution for scaling up the cutting process of lithium metal, the ideal laser type to be used for this operation still requires further attention. Accordingly, this work investigates impact of continuous wave and ns-pulsed laser sources on the cut quality and productivity of 50 µm-thick pure Li sheets. Processing conditions are discussed to address the environmental control issues for reactivity along with the different processing regimes observed.

This study highlights a groundbreaking advancement in Direct Laser Interference Patterning (DLIP) by integrating a high-power multimode fiber laser, traditionally used for macro fabrication, into precision microfabrication processes. By employing an innovative beam-shaping system, the challenges associated with the low coherence and beam quality of multimode lasers are effectively addressed, enabling the generation of well-defined periodic structures on large surface areas. This novel approach demonstrates the feasibility of utilizing multimode fiber lasers for high-resolution microstructuring, thus marking a significant shift in their application scope. The findings open new opportunities for integrating these versatile and high-power lasers into industrial-scale microfabrication, offering efficiency, scalability, and precision.

Laser cutting of electrode foils is a critical step in Li-ion battery manufacturing, with high single-pass speeds along with excellent quality being required. While demands have previously been met by infrared fiber laser technology, producers are increasingly turning to high-power ultrashort pulse (USP) lasers as quality requirements continue to increase. In this work, we present results for laser cutting graphite-based anode and NMC cathode battery materials. The foils are ~100 µm thick and double-side coated with the respective active material. Using 200 watts of IR femtosecond laser power, single-pulse cutting processes were developed and optimized, followed by a burst-optimization scheme using the laser’s flexible pulse-tailoring capability. When bursts were optimally applied, cutting speeds improved by up to ~45%. Analysis includes optical and scanning electron microscopy, with particular attention given to the cut edge quality and the amount of excess active coating material removal.

In High-Speed Laser Blanking for automotive production, efficiency is evident compared to traditional methods like stamping, as tool changes and prototype development are eliminated. Continuous processes in laser beam cutting require reliable detection of process boundaries to prevent downtimes and enhance productivity. AI-based real-time monitoring can optimize speed safety margins. Key technologies such as Minimal Invasive Laser Power Modulation (MILM) facilitate precise process monitoring and cut failure detection. A Convolutional Neural Network (CNN) achieves a classification accuracy of 97.9% and ensures real-time capability in operation. In application, the error rate of this classification result can be further reduced by implementing a hysteresis function to increase classification reliability, avoiding unnecessary downtime and opening up avenues for further process optimisation.

Precision in manufacturing has become essential in today’s competitive market, necessitating the minimization of all sources of inaccuracies. In the laser cutting process, the inherently thermal nature introduces significant heat to the workpiece, causing thermal expansion and dimensional errors in the absence of compensating strategies. These issues are particularly pronounced in aluminum tube workpieces due to their high thermal conductivity, large expansion coefficient, and extended axial dimensions of the raw material, which amplify thermal expansion effects. This study addresses these challenges by developing a real-time-capable predictive dynamic model. The model correlates commanded laser power with average heat-induced temperature increase, enabling precise, workpiece-specific thermal expansion estimation while maintaining computational efficiency. Calibrated and validated on an industrial laser tube machine, the proposed strategy achieves an average error reduction up to 75%, significantly improving dimensional accuracy and offering a robust solution for high-precision laser-based manufacturing.

To meet stringent requirements in terms of productivity and efficiency, the industry is shifting towards machine tools with sensors and auto-tuning capabilities enabled by Artificial Intelligence (AI) algorithms. Accordingly, in laser cutting the coaxial monitoring of the molten pool provides relevant information that can be interpreted by means of Machine Learning (ML) approaches to enable real-time velocity-based feedback control. In the present research, a holistic control architecture was thus developed and validated on an industrial case-study to demonstrate its applicability. Targeting iso-quality conditions, experiments on sample geometries on 5 mm thick stainless steel allowed to showcase an increase in productivity whilst avoiding critical defects such as cut dominated by plasma formation or loss of cut. The results obtained may be extended to a wide range of materials and sheet thicknesses demonstrating the generalized applicability of the technological framework.

Laser piercing is the initial phase of laser cutting, where a focused laser beam creates an entry hole in the material for subsequent cutting. This process is particularly challenging in thick stainless steel plates, as it requires precise control of energy input: excessive energy causes melt accumulation and process failure, while insufficient energy prolongs piercing time, reducing productivity. Prior studies demonstrated that time-varying pulse sequences can significantly decrease piercing duration, but identifying the optimal sequence within a few trials remains unresolved. This work presents a Bayesian optimization approach to minimize piercing time, demonstrated on 30 mm thick stainless steel plates with a 12 kW industrial solid state laser. To further refine the process, we integrate physically motivated strategies into the optimization framework. Our findings show that incorporating this additional knowledge can reduce the number of required optimization iterations, ultimately enhancing productivity in laser cutting operations by shortening process times.

Transparent laser welding using femtosecond pulses offers a promising solution for precise joining of glass materials. In this study, we demonstrate the successful assembly of large-diameter (20 mm), crack-free fused silica using femtosecond laser welding, without the requirement of chemical pre-treatment or adhesives. A microscope objective, with a numerical aperture of 0.26, was used to focus the laser at the interface, generating a highly localized and intense spot for precise melting of the material. Using a femtosecond laser with a pulse energy of 60 µJ, a repetition rate of 200 kHz, and a scanning speed of 10 mm/s, the spiral pattern minimizes overprocessing and reduces stop-start points, ensuring uniform energy deposition. This approach produced defect-free welds, contributing to improved mechanical resistance, as demonstrated by tensile testing. These results demonstrate the potential for transparent laser welding to be adopted for industrial applications in optics, photonics, and high-precision manufacturing.

Glass welding using femto-second lasers conveys numerous advantages compared to the usual glass joining technics such as better resistance to high temperature and no requirement for an extra intermediate material. However, it requires an optical contact between the two glass plates to weld. This poses constraints on the flatness and rugosity of the glass plates. We demonstrated that using the burst mode of the laser combined with a long focal lens can help to overcome this restriction by allowing a welding despite the gap with high speed (up to several meters per second). We’ve been able to weld two glass plates with a gap of 3 µm with a scanning speed of 2 m/s. The mechanical resistance of the welding will also be discussed.

Ultrashort pulsed laser welding is of significant interest for manufacturing precision optical systems. Typically, the process employs a high numerical aperture (NA) lens to focus the laser near the interface, providing a sufficiently high energy density to confine thermal energy and reduce unwanted non-linear effects (e.g., damage) above the desired focal region. However, high NA focusing cannot be readily combined with high-speed scanning, resulting in slow process rates with typical translation speeds of a few mm/s.

In this presentation, we demonstrate that welding is possible at higher speeds using a 167 mm focal length telecentric lens (providing an NA of 0.03). This lens, in combination with a galvanometer scanhead, enables much higher process rates. However, material cracking can be an issue, depending on the material combination and processing parameters. We present results of successful welding of Silicon-BK7 and AlSi-BK7, including measurement and analysis of stress-induced birefringence.

The GHz-burst mode, a relatively new regime in femtosecond laser processing, offers a novel solution for joining dissimilar materials. Its unique way of energy deposition within materials makes it an excellent candidate for the transparent welding of metal and glass. This study investigates the feasibility of this approach, addressing the challenges posed by the differing physical and chemical properties of the materials. Experimental results reveal the formation of strong, defect-free interfaces between silica and copper or steel assemblies, attributed to precise energy deposition and minimal thermal impact. This innovative approach to dissimilar material assembly combines the best characteristics of each material, offering promising potential for advanced applications in the fields of electronics, optics, and photonics.

The production of practical, miniaturized pipelines that allow liquids to flow smoothly presents numerous challenges. Coatings are usually applied to the inner walls of the pipes. An innovative approach involves the use of high-precision laser processing. The utilization of USP laser processing is used both to create functional surfaces and to produce miniaturized pipes through overlap welding process. In the context of the conducted investigations, results on overlap welding with two non-transparent thin foils with USP lasers are presented here. In this study, we conducted overlap welding on two 20 µm thin 1.4301 stainless steel foils using a ps-burst laser. We present insights into the optimal process parameters and the influence of sample preparation. The parameters are evaluated in terms of power density, weld quality, reduced heat-affected zone (HAZ), and reproducibility of the welding results.

Ultrashort pulsed laser welding presents an attractive alternative to the adhesive bonding currently used for bonding metal to optical components in the manufacture of precision optical systems. However, this process has lacked a standardized surface preparation methodology to ensure high yield and high-quality bonding. To address this, we have developed a multi-stage preparation process for stainless steel SS316 and tested its general applicability with three related metals: the controlled expansion alloys Invar, Kovar, and Inconel.

In this presentation, we showcase the welding results achieved using this preparation methodology. Each alloy was bonded to an optical material with closely matched thermal expansion: Invar to fused silica, Kovar to BK7, and Inconel to quartz. These material combinations are crucial for optical applications operating over a broad temperature range to minimize stress-induced birefringence.

Direct Laser Interference Pattering (DLIP) has evolved as an efficient method for surface functionalization by producing periodic structures. When using femtosecond or picosecond laser sources, the produced topographies are also covered by Laser Induced Periodic Surface Structures (LIPSS), being its orientation controlled by the polarization direction of the beam. On the other hand, the orientation of the LIPSS has an effect not only on the geometry of the produced patterns, but also in the ablation efficiency during the structuring process. In this work, stainless steel 304 and aluminum 2024 plates are treated with 12 ps and 70 ps laser pulses (1064 nm) using DLIP, producing line-like structures with 6.0 µm and 5.4 µm periods when rotating the polarization direction and thus the LIPSS orientation. It was found that the ablation efficiency can be improved significantly when the LIPSS are perpendicular to the DLIP features.

The characterization of laser-textured periodic surface topographies, such as Laser-Induced Periodic Surface Structures (LIPSS) and Direct Laser Interference Patterning (DLIP), plays a key role in the advancement of material functionalities in various industries. In this work, we present an innovative FFT-based device that uses diffractive methods for accurate real-time analysis of complex surface patterns. This non-invasive and scalable approach is adaptable to different substrates and pattern types and offers a significant improvement in quality control over traditional techniques. By integrating Fourier transform analysis with diffraction-based measurements, the device provides an accurate determination of spatial frequencies, periodicity, and deviations in surface textures, critical parameters for optimizing laser fabrication processes. Experimental validation confirms the device reliability in characterizing LIPSS and DLIP structures and demonstrates its potential for practical integration into industrial laser-based manufacturing systems.

Laser Surface Texturing (LST) has emerged as a powerful solution to provide materials with specific functionalities. By creating surface textures and patterns, tailored surface properties can be achieved for distinct applications such as controlling of wettability and optical properties. To boost the implementation of LST at industrial scale, we have investigated the use of a high-power ultrashort pulse laser (USPL) combined with advanced beam shaping technologies as a robust, high quality and highly productive solution for generating functional patterns on different materials.

In particular, we present the laser surface functionalization of both plastic and metallic components for industrial applications. For example, the laser surface texturing of steel inserts for plastic moulding, decreasing the wettability of the material and obtaining hydrophobic properties. In another example, the laser surface texturing of polymer materials, modifying optical properties such as opacity and haze.

There are several challenges when considering surface functionalisation in complex industrial parts. To give an answer to them, BILASURF European Project is developing and integrating a system for high-rate laser functionalization of complex 3D surfaces using tailored designed bio-inspired riblets to reduce friction and improve the environmental footprint of industrial parts, ensuring a high throughput with the help of inline monitoring capabilities. The technology will be demonstrated in hydraulic turbines and industrial fan injection molds, and the integrated system will include two technologies: DLIP (for riblet periods up to 50 µm) and DLW (for riblet periods above 50 µm). Picosecond regime has been used to develop both processes, as the final system will include a single laser source for DLIP and DLW. In the case of the DLW process, an increase of the ablation rate by a factor of four has been achieved using a 1 MHz frequency and burst-mode.

In recent years, surface functionalization through topographical modifications has attracted significant attention for controlling wettability. Among the different technologies available, laser texturing has emerged as a particularly promising technique due to its ability to create micro- and nanometric structures with high precision, repeatability, and automation. However, achieving a specific wettability often requires an iterative trial-and-error approach. This study proposes a methodology to accelerate the selection of the most appropriate texture to control the wetting of polypropylene. This method includes an ultrafast laser parameter optimization process and the identification of the key dimensional factors influencing the contact angle variation through the development of tens of different textures, combined with a CFD Two Phase flow simulation model. By establishing the relationship between texture parameters and wettability, these findings contribute to the rapid development of functional surfaces in polypropylene.

Femtosecond laser processing is an effective technique for modifying polymer surfaces, enabling precise control over topography and chemistry for advanced applications, such as biomedical devices, microfluidic systems, and electronics. This study compares the effects of femtosecond laser irradiation using infrared (IR) and ultraviolet (UV) sources on polymer substrates, focusing on changes in surface wettability and chemical transformations. Surface wettability has been characterized by contact angle measurements, while morphology was analyzed using optical profilometry. IR irradiation induces deeper surface modifications through multiphoton absorption, while UV irradiation results in finer, shallower changes through single-photon absorption. These structural and chemical differences lead to distinct wetting behaviors, depending on whether the polymer is treated with UV or IR laser irradiation. Chemical analysis reveals distinct photochemical pathways activated by each laser source, providing valuable insights for tailoring polymer surface properties.

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Beam shaping is a critical technique for optimizing laser performance in industrial manufacturing but the high thermal loads of the laser limits the development of optical beam shaping systems to few systems able to produce a single basic shape.

We present a groundbreaking adaptive beam shaping system based on a deformable mirror that produces multiple shapes by dynamically correcting the wavefront distortions in real time. The closed-loop control is assured by a low power laser separated from the high power laser path whereas an active cooling stabilizes the temperature of the mirror when irradiated by laser up to 4 kW.

Our technology represents a versatile solution matching multiple needs of laser manufacturing processes and boosting their productivity and quality.

The presentation will highlight the system design and the results of preliminary tests.

Laser welding is widely used in electric vehicle manufacturing but faces challenges like weld defects and instability at high speeds. Laser beam shaping has emerged as a promising solution. This study investigates the impact of both static and dynamic beam shaping techniques on weld quality in e-mobility applications. Using detailed computational fluid dynamics (CFD) simulations, we analyze how different beam intensity profiles influence melt pool behavior, fusion zone geometry, and keyhole-induced porosity. The model includes complex physical effects such as multiple reflections, phase transitions, surface tension, buoyancy, and Marangoni flows. Results show that beam shape significantly affects maximum and average temperatures and velocities inside the melt pool which relate to process stability, spatter, and pore formation. These insights support the development of optimized beam profiles for improved welding performance in automotive applications.

The ongoing electrification of drives is increasing the importance of processing copper materials, particularly in welding. A highly automatable and flexible joining method for copper materials is laser welding. Literature indicates that the process can be stabilized using laser radiation in the visible wavelength range or through beam oscillation.

This paper describes the concept and design of a new beam source with a 532 nm laser beam wavelength at the highest beam quality and with up to 500 W laser output power. This was achieved using a coherent beam combination in the green wavelength range, the CBC-green-laser.

The use of this novel high-brilliance continuous-wave laser source in the visible range was inves-tigated in comparison to established remote laser methods using near-infrared radiation and ex-amines the benefits of 532 nm wavelength for highly reflective copper materials. This provides users and developers with validated insights for future developments in the e-mobility market.

Owing to the complex clamping requirements, accurate positioning and limited available area for processing, welding can be classified as a critical process in manufacturing of metallic bipolar plates. A shielding gas assisted welding process is used for isolating oxygen from the process zone and to help reduce weld spatter. The gas flow rate can influence the dynamics of melt pool and material solidification which may aid to improve the seam quality. A system was developed for local provision of the gas during the laser welding of bipolar plates. The system can be attached to the clamping fixture to ensure even distribution of the gas in targeted locations and allows the adjustment of the gas flow rate as per requirement. Various shielding gas supply configurations were tested to verify the most effective design for optimal distribution of the gas and cross-sections of weld seams were compared.

Micromachining of quartz presents significant challenges due to its chemical inertness, high melting point and optical properties. Usually, structuring processes such as lithography in combination with wet chemical etching or RIE etching are used. These allow a high processing quality, but the variety of possible geometries is severely limited by the 2D pattern transfer. Conventional techniques such as micro-grinding and milling are limited to larger dimensions. Excimer lasers, emitting ns-pulses in the UV, enable high-quality microstructures but are mostly used for surface texturing or realization of simpler geometries due to beam characteristics. The third harmonic of a femtosecond laser (fs) offers precise processing with minimal thermal effects, allowing direct writing. This work demonstrates the fabrication of a complex quartz platform, providing experimental insights into cutting and structuring. The findings highlight the viability of femtosecond laser technology for high-quality micromachining of quartz platforms in advanced applications.

Transparent materials, such as glass and crystalline substances, are essential for optical interfaces in many technical and medical applications. The integration often requires the connection of the glasses with a metal structure. Established technologies such as adhesive or anodic bonding require a large contact area to achieve sufficient strength. Ultra Short Pulse (USP) laser welding can overcome these difficulties and offers precise, low-thermal impact joining of glass to metals without an intermediate bonding material.

Our previous studies have shown promising results, achieving average shear strengths over 50 MPa for glass to aluminum foil bonding. Here, we will discuss transferring our robust welding process to various metal foil combinations, extending the benefits of USP laser welding. Our findings suggest our approach can be adapted to a wide range of materials, opening new possibilities for industrial and medical applications requiring durable and precise assemblies.

The GHz-burst femtosecond laser regime has attracted growing interest for its applications in glass percussion drilling. In this work, we introduce an innovative GHz-burst femtosecond laser (800fs, burst energy >0.3mJ) ) operating at a green wavelength (515 nm), uniquely capable of generating arbitrary burst shapes. This advanced laser system unlocks new opportunities for optimizing ablation processes in glass percussion drilling. By combining the advantages of the green wavelength with tailored GHz burst profiles, we demonstrate that the interaction between the laser and the glass is significantly improved, resulting in faster drilling and higher-quality holes with smoother surfaces and absence of cracks. This approach lays the groundwork for advancing the understanding of GHz-burst laser processing and its transformative impact on glass drilling techniques

The demand for micrometric through-holes in glass and silicon carbide (SiC) is growing, particularly in advanced packaging and power electronics. While selective laser etching (SLE) remains the dominant method for through-glass vias (TGVs), environmental concerns and process complexity highlight the need for alternatives. One option is percussion drilling, but it faces challenges such as drilling saturation due to the conical shape of the hole, microcracks, and stress. Recently, GHz burst processing has attempted to address these issues, but some fundamental limitations remained. In this study, we showcase the unexplored potential of repetitive single-pulse femtosecond laser drilling. Using optimized focusing conditions and a femtosecond fiber laser with >200 μJ pulse energy and 250 fs duration, we achieved full penetration of up to 1 mm - thick glass and fast SiC drilling. We also demonstrate a method of multiple-hole drilling speed improvement enabled by an advanced pulse-on-demand laser feature.

Ultrafast laser ablation has been proven to allow for the generation of micromechanical devices, micro-optics and microfluidics. To successfully transfer this approach towards an industrial level, process efficiency and stability as well as resulting parts quality have to be improved. Here we report on the reproducibility and enhanced accuracy of 2.5D ultra-short pulsed laser ablation of fused silica to structure complex optics by integrating center recognition and height measurement within an automated machine setup and by sensitive adjustment of the applied laser parameters to optimize the ablated depth per path in multi-pass ablation processes. To exemplify the potential of these approaches, free-form optics and axicons are generated with improved geometrical and surface characteristics.

Laser polishing of glass using a CO2-laser beam is a contact-free alternative to mechanical polishing of optical surfaces. However, this process suffers from mid-spatial frequency errors (MSFE, 80 µm ≤ λ ≤ 2500 µm). This work presents experimental investigations into the formation of MSFE during laser polishing. Using a controlled variation of the process temperature during laser polishing of fused silica, in addition to the expected densification process, a nanoscale ablation process occurring below the evaporation temperature is observed. This ablation process first occurs at a process temperature of around 1950 °C, resulting in an ablation depth of a few nanometers, which increases to several hundred nanometers when approaching the evaporation temperature. As a result, due to fluctuations in the laser power during laser polishing, inhomogeneous ablation occurs, leading to the formation of MSFE. By utilizing a closed-loop temperature control or reducing the process temperature this issue can be mitigated.

Even though process simulation for 3D printing has progressed substantially over the past decade and across multiple length-scales, the major issue is about how to link these simulations and then perhaps to combine these models with topology optimization for getting an improved design under the umbrella holistic computational design. The solution is multi-scaling laws which are; homogenization, material multi-scaling and process multi-scaling. The first two multi-scaling techniques allow for extracting macroscopic properties of an entire part based on the data generated by process simulations at lower dimensions, namely micro- and deposition-scale models while process multi-scaling methods enable fast computation of a real-size sample and such models can be improved by involving material multi-scaling . Finally, this holistic model can be incorporated into the topology optimization calculations for a far better design of a part with ultimately no sign of process-induced defects, under the flag of physics-aware topology optimization.

Laser Metal Deposition (LMD) is an additive manufacturing process that utilizes a focused laser beam to melt and deposit powder onto a substrate, enabling the layer-by-layer creation of complex geometries. This study investigates dynamic beam shaping to enhance resource efficiency in LMD, particularly when processing intricate geometries. While conventional Top-Hat and defocused Top-Hat profiles are commonly used, adjusting the laser intensity distribution can improve process quality, especially when dealing with small powder and laser spot diameters. A modified laser intensity distribution alters the melt pool dynamics, thereby influencing the powder utilization rate. A measurement setup is employed to determine the focal position and diameter of the powder stream, allowing for the selection of appropriate boundary geometries for the beam profile. Dynamic beam shapes are then applied coaxially through the powder nozzle. This novel approach results in improved powder utilization rates compared to traditional Top-Hat profiles.

Pure copper exhibits excellent antimicrobial properties, and the pure copper coating on surface such as doorknobs or handrails can effectively prevent the spread of infections. We have developed a high-quality pure copper coating with blue diode lasers for an efficient copper processing method, and employing multibeam laser metal deposition to create a thin layer with a thickness of around 100 µm and the high adhesive strength. However, the circular beam with a spot diameter of 233 µm, much smaller than the powder flow diameter, was previously used, resulting in low layer formation efficiency. To address this, a rectangular beam with a spot size of 584.7 µm×1059 µm was introduced. As a result, a pure copper coating with a thickness of 122.2 µm and a surface roughness of 6.16 µm was formed. Compared to the same quality coating using a circular beam, the layer formation efficiency increased by 3.22 times.

This study investigates the application of a novel deformable mirror system for beam shaping in laser-based welding and directed energy deposition, emphasizing process improvements and robustness. In directed energy deposition, the effects of three near-elliptical Gaussian beam shapes on melt pool and bead geometries were analyzed. The beam shape with the major axis aligned to the wire feeding direction, featuring the highest average power density and intermediate peak power density, provided reduced bead geometry variation and enhanced process stability. For butt joint welding, the system was used to elongate the focused laser beam into elliptical shapes. This approach reduced the sensitivity of the fused zone’s dimensions to joint gaps, minimized the heat-affected zone, and decreased undercuts. The findings demonstrate the potential of beam shaping to enhance robustness, reduce defects, improve energy utilization, and boost productivity in high-power laser processing applications.

This study investigates the application of Optical Coherence Tomography (OCT) for real-time monitoring of the 3D-EHLA (3D-Extreme High Speed Laser Metal Deposition) process. The OCT enables precise measurement of layer thickness and immediate detection of process deviations. The results confirm the capability of OCT to consistently monitor the layer heights at deposition speeds up to 200 m/min. While this project focuses on monitoring, the findings suggest that OCT can also be reliably used for feedback control in future implementations. This integration enhances the reliability of the 3D-EHLA process and supports its implementation in industrial environments. The use of OCT provides a robust solution for addressing the challenges of high-speed additive manufacturing, ensuring product integrity and process efficiency.

Laser welding in e-mobility presents significant challenges, particularly for copper and aluminum joints, due to their high reflectivity, thermal conductivity, and susceptibility to defects like porosity or cracking. Optimizing the energy distribution within the laser beam is key to stabilizing the melt pool and improving weld quality.

We introduce a unique beam-shaping solution that generates a four-spot pattern to enhance aluminum battery pack welding. This approach is implemented on a universal platform compatible with all laser sources. Various four-spot configurations will be analyzed, with welding performance systematically compared to the unshaped beam.

Laser beam welding is a very efficient process for joining two copper hairpins in electric drives, known as hairpins. The occurrence of welding defects reduces the quality of the weld. Pores, for example, reduce the conductive cross-sectional area, which increases the electrical resistance and further impairs the strength of the connection. In addition, complex testing procedures as for example computational analyses must be used to ensure that each individual weld meets the quality criteria. This is why this work focuses on in- process measurements to detect defects, such as pores. For the investigation optical coherence tomography was used to investigate in the detection of welding defects during the welding of these hairpins. Computational analyses (CT) and high-speed videos were used to determine the context of the optical coherence tomography signal and the weld result. It was found that optical coherence tomography is a good method to determine defects real-time capable.

Demand for precise measurements of high-speed laser welding depth is increasing due to growing e-mobility applications. Optical coherence tomography (OCT) can measure keyhole depth in real time. Newer fiber laser generations, ideal for such applications, offer single mode core/ring configurations. However, OCT’s usability with small keyhole apertures may cause measurement inconsistencies. This work proposes a systematic analysis of signal behavior using a contemporary fiber laser with a single mode core and a ring with separate power control, producing focal core and ring sizes of 40 µm and 285 µm, respectively. Bead-on-plate experiments were conducted on 5 mm thick EN AW-1050 Al-alloy. Core and ring power levels were systematically analyzed along with scan speeds. The OCT focal beam of 35 µm was aligned with the laser beam for different scan speeds. Keyhole depth was compared to molten seam depth from metallographic cross-sections. Feasibility windows for stable OCT measurements were identified.

Optical coherence tomography (OCT) can be used to determine the depth of the keyhole during laser deep penetration welding. However, due to the nature of the OCT data a statistical evaluation approach is necessary, reducing the possible temporal resolution. At the same time, keyhole welding is a strongly dynamic process and the penetration depth of welds can fluctuate even under constant process parameters. In this study the time scales on which weld penetration depth deviations can be detected are investigated by examining longitudinal cross sections of weld seams and comparing to the corresponding OCT measurements. Differences between the Materials Steel (S235JRC), Aluminum (EN AW-5083) and Copper (Cu-ETP) are examined. Results show that OCT measurement frequencies are high enough for spontaneous weld depth deviations to be recognized with sufficient precision. Thus, controlling the laser power to achieve a more uniform weld depth driven by real-time OCT measurements is a plausible approach.

Sustainability is becoming increasingly important in production of vehicles. The e-mobility transition has shifted the CO2 footprint from use to production phase, where secondary alu-minum alloys in structural castings are known to offer significant CO2 reduction potential. However, accumulation of copper, iron and zinc and the hydrogen content in the melt pose major challenges for casting and subsequent joining processes. In laser welding, dynamic modulation of intensity distributions in the weld pool can overcome the latter issue. In experi-mental studies covering high pressure die cast AlSi10MnMg alloys with secondary material content levels ranging from 0 wt.-% to 89 wt.-%, castability and weldability were investigated and the structural and mechanical properties of the joint determined. The results contribute to the optimization of sustainable car body production methods, providing a path towards cost-effective differential lightweight design solutions as economically, technologically and ecologi-cally competitive alternatives to large-scale casting technologies (giga-casting).

The LMJ laser is a major scientific facility dedicated to High-Energy Density Physics Experiments. The laser-target interactions produce dense and hot plasmas in a few nanoseconds only.

Targets are designed and manufactured by the authors. Their fabrication is a continuous challenge, as they are composed of many – specific and innovative – materials shaped and assembled in a sub-millimeter range. They must meet stringent specifications, which requires the development of high-tech fabrication processes. In this field, laser micro-machining processes offer reliable and accurate solutions, whether it is for 2D or 3D micro-machining, drilling, selective ablation or micro-welding.

During this oral talk, we give an overview of the latest developments in laser micro-machining of targets components, involving both nanosecond pulses (excimer laser) and ultrashort pulses (femtosecond laser). We will emphasize on the quality, accuracy and specificity of our machining – that require a deep understanding of the materials and processes involved.

The application prospects of high entropy alloy nanoparticles (HEA NPs) are closely tied to their structure, chemistry, and the scalability of their fabrication method. This talk introduces the pulsed laser synthesis of nanoparticle colloids, composed of up to six elements. It demonstrates how tuning the elemental composition influences their activity in heterogeneous catalysis, relevant for green hydrogen production and fuel cells. The laser pulse duration allows to pre-set if the HEA NPs are crystalline or amorphous, and the particles are highly robust, as shown by their outstanding temperature stability. Significant up-scaling is achieved through continuous flow synthesis using a high-power ultrafast laser system, resulting in productivities equivalent to kilogram-scale heterogeneous catalysts. Furthermore, reproducibility is ensured by an automated benchtop system that has recently been commercialized.

Stripping the remanent protective coatings on engine-worn gas turbine parts is the first step in the process of turbine refurbishment. Coat stripping is usually carried out using multiple cycles of forced mechanical abrasion followed by chemical treatment. This method has proved to be significantly inefficient regarding process time and energy consumption, in addition to the associated health and safety hazards and adverse environmental effects due to chemical waste disposal.

Here, we report on an alternative method to strip turbine diffused aluminide coatings using nanosecond laser irradiation. The material removal rate of the coating was analysed with varying laser fluence, scanning speed, and overlap after the determination of the damage thresholds of the coating and the metallic substrate. The depth of ablation and the grain structure of the underlying substrate were determined to assess the effectiveness of the process and the condition of the substrate after laser irradiation.

Strain influences the band structure, and therefore the optical properties of semiconductors. In case of GaAs quantum dots, the deliberate introduction of strain can modify the emission characteristics by compensating the exciton fine structure splitting, thereby optimizing the entanglement between the polarization degrees of freedom in a biexciton cascade. However, this application requires a complex multi-axis actuator which can be operated at cryogenic temperatures. The most promising material for this application is monocrystalline PMN-PT which exhibits giant piezoelectric behaviour. Nevertheless, the mechanical and chemical properties of this material limit the processing methods for realising complex geometries. In this work, we show that a combination of layer structuring, thinning and cutting, enables an entirely fs-laser-based realisation of this important component for quantum optics. In addition, the dimensions of this strain-tuning device can be miniaturised by using UV-fs-laser pulses, which is a first step towards multiple quantum emitters on a single chip.

Ultrafast lasers are essential for microfabrication, offering precision and minimal thermal damage. In 2016, the GHz burst regime gained interest because of its ability to increase ablation throughput while maintaining precision. Later studies revealed that the efficiency highly depends on burst parameters and material properties, making necessary more investigations.

We studied ultrafast laser ablation of copper and silicon using bursts with intra-burst repetition rates ranging from 1 GHz to unexplored values up to 15 GHz, using 15 different burst configurations. We show that the highest repetition rates are more efficient for copper ablation. In contrast, silicon lower thermal diffusivity makes the effect of the repetition rates negligible. Moreover, the crater morphologies suggest a link with the viscosity of the liquid phase, providing insights into the temperature reached during ablation. Finally, multi-burst processing shows a drastically different behavior from single burst: efficiency and crater profile strongly depend on the burst parameters.

Stainless steel alloys are an essential material in industrial applications due to their excellent corrosion resistance and mechanical properties. However, variations in chemical composition, thermal diffusivity, and microstructure significantly influence laser processing outcomes. This study focuses on the impact of the energy distribution within burst trains of pulses on the ablation efficiency and surface quality of AISI 304, AISI 420, and AISI 316Ti. Using an ultrashort pulsed laser with a 250 fs pulse duration, rectangular cavities are produced at various fluence levels and different burst configurations with different intraburst energy distribution. Using burst modes demonstrated improvements in both removal rate and surface quality. In addition, the variation of intraburst energy distribution showed a significant impact, for example at 9 J/cm² and MHz burst with a positive and negative slope, ablation rates of 1.1 and 1.8 mm³/min were reached, with Sa values of 4.5 and 2.9 µm, respectively.

The choice of process gas plays a pivotal role in determining the properties of materials processed by laser-based additive manufacturing. By strategically combining process gases and materials, manufacturers can not only tailor hardness and dilution but also reduce operational costs—key factors for advancing industrial laser materials deposition (LMD) applications. In this study we investigate the impact of various process gases on laser material deposition process, emphasizing their effects on melt pool dynamics, microstructure, layer quality, hardness, and process costs. Using 316L powder, a disk laser, and the process gases argon, helium, nitrogen, and CO₂, we conducted experiments analyzing single track geometry, hardness, microstructure, and deposited volumes. The results highlight CO₂ as a distinct process gas, exhibiting unique effects on dilution, microstructure, and hardness that set it apart from the other gases and offer potential for tailored applications.

Powder properties are considered an important factor for part quality in additive manufacturing using lasers, although few studies have investigated effects in directed energy deposition (DED-LB). Water atomized (WA) and gas atomized (GA) powders are frequently used but may lead to different part properties due to differing powder properties. To examine their qualification for DED-LB, this work examines GA and WA powders of AISI 316 and build quality. Results show that the atomization method shows no relevant influence on porosity and Archimedian density of built parts. Also, WA powders show good processability in DED-LB, despite unfavourable morphology. In contrast to this are mechanical properties: WA specimen reach only 9 % elongation where GA based reach 33 %. Tensile strength of both are below 580 MPa. As a reason, defects and oxides can be assumed. Cheaper WA powders with less favorable morphologies could still be used for DED-LB, when load requirements are low.

In laser-based directed energy deposition (DED), a well-aligned powder stream relative to the laser beam is essential for maximizing process efficiency and minimizing material loss. A detailed understanding of powder stream propagation is therefore critical. In this study, high-speed imaging was used to investigate particle behavior within the powder stream. Using a multi-step evaluation method, the mean velocity, velocity variations, and flight direction of individual particles were determined. Powder channels with varying surface roughness—ranging from Ra = 2.16 µm to 0.27 µm—were tested to assess their influence on stream characteristics. The results reveal that lower channel roughness leads to increased mean particle velocity and significantly narrower flight angles. Specifically, the divergence angle decreased by approximately 61%, which suggests the potential for a more focused powder stream and reduced material loss. These findings offer valuable insights into optimizing powder delivery systems for enhanced efficiency and precision in laser-based DED processes.

EN AW-7075 (AlZn5,5MgCu) is a high strength aluminum alloy for aerospace applications suffering from poor weldability due to solidification cracking susceptibility. In this study, crack free Laser Metal Deposition (LMD) of EN AW-7075 is enabled by adding up to 1 %vol of TiC-nanoparticles (35-55 nm) to the powder feedstock. It was found that nanoparticles are successfully incorporated into the melt pool where they provide for a grain refinement due to inoculation, and thereby eliminate hot cracking.

Moreover, the addition of nanoparticles enhances the absorption of the laser wavelength in the powder (as measured with an Ulbricht sphere) and was found that the incoupling efficiency of the processing laser beam was increased which affects the melt pool dimensions and further helps to prevent lack of fusion defects in processes with the same parameters.

There is currently a requirement of the market to produce brake disks which produce minimum fine dust emissions: the euro 7 emissions rules for automotive sector. For this reason, it is necessary to improve the wear resistance of the brake disk.

A wear coating using EHLA (Extreme High-speed Laser Application) is one of the most popular solutions, however, it has been observed that the adherence between the coating and the material of the brake disk, is usually poor due to the presence of lamellar graphite in the cast iron.

This work presents an optimized laser pre-cleaning process of the brake disk surface prior to the application of EHLA. Coating experiments using 430L were performed with and without laser pre-cleaning. The results of the experiments demonstrate that the pre-cleaning removes graphite from the surface and reduces the porosity in the coating, thus achieving an improved metallurgical bond between the two materials.

Additive manufacturing (AM) of steel is gaining traction in the construction industry, offering the ability to fabricate complex geometries and optimize resource use. Among the AM techniques, Laser-Based Powder Directed Energy Deposition (DED-LB) is notable as it provides a compromise of relatively high productivity with respect to powder bed fusion and fine resolution with respect to arc based DED processes. However, the common steel grades often encounter challenges in meeting construction requirements, including limited compatibility with conventional structural steels concerning bolted and welded assemblies. This study tackles these challenges by developing the DED-LB process with a novel high-strength steel powder feedstock. Through an extensive experimental campaign, the research evaluates the processability of the material, focusing on achieving dense and crack-free steel components. The results highlight optimized deposition strategies providing high mechanical strength, opening new possibilities for its adoption in the construction sector for medium to large sized products.

Laser-Induced Forward Transfer (LIFT) achieves high-precision 3D cell immobilization within extracellular matrices using a sub-ns Nd:YAG laser. Rheological analyses and dynamic imaging optimize biofabrication, showcasing potential applications in regenerative medicine and tissue engineering.

Industrial ultrashort pulse laser advancements culminate in the 1-kW-average-power TruMicro 9000 laser, delivering up to 10 mJ pulses. Diffractive beam splitting increases throughput significantly, but spatio-temporal distortions require careful compensation for industrial-scale ultrafast processing.

In our reserch, we demonstrated that the formation of laser-induced periodic surface structures (LIPSS) in air and nitrogen atmospheres on the surface of aluminium current collectors allows a significant reduction in cell resistance.

Pump-probe microscopy (PPM) is a powerful technique for investigating ultrafast laser ablation. However, establishing a quantitative link between transient optical signals and final-state measurements remains challenging. This study addresses the issue by examining the ablation dynamics of austenitic stainless steel AISI 304 and the high-entropy alloy CrMnFeCoNi.

Transfer-matrix analysis of PPM measurements reveals that Newton ring contrasts provide a quantitative assessment of the spallation layer thickness, showing good agreement with final crater depths. Temporal signatures offer a clear window into the formation and disintegration of the spallation layer. The lower ablation efficiency of AISI 304, compared to CrMnFeCoNi, is attributed to an enhanced photothermal contribution, leading to a more pronounced ablation plume. This effect is evidenced by higher absorption and, consequently, reduced Newton ring contrasts.

These findings demonstrate the potential of PPM to quantitatively link transient dynamics to final-state observables, advancing the understanding of laser-driven processes.

Pump-probe microscopy is an essential tool for studying laser-matter interaction. However, the imaging of laser-induced surface acoustic waves (SAWs) has not been possible with a conventional setup. In this study, we present a new approach to detect laser-induced SAWs on silicon and thin metal films with a conventional setup and discuss the mechanisms behind it. To detect the SAWs, the focal plane of the probe beam has to be shifted into the microscope objective. In doing so, nonlinear absorption or Kerr lens focusing inside of the objective could act as a background filter or dark field mode. In the future, this effect could provide new insights into the phenomena of laser-matter interaction, photoacoustic effects, especially at high intensities, and materials science.

With pulsed laser ablation in liquid ligand-free nanoparticles from virtually any material can be produced. Recent developments in the process design allowed the technique to reach gram per hour nanoparticle productivity. However, little attention has been paid to how the alteration of the laser ablation dynamics by the presence of the liquid layer influences ablation efficiency. For this, we connect results of pump-probe microscopy and absorption corrected ablation efficiency measurements. The time-resolved experiments demonstrate redeposition, which up until now was only shown by computational methods. In conjunction with the efficiency measurements this allows to determine that more than 80% of the ablated material is redeposited. Our results demonstrate that redeposition during laser ablation in liquid fundamentally limits ablation efficiency. Based on this, strategies such as employing double pulses or using microparticles as target materials may be formulated to reduce redeposition, increase ablation efficiency, and further scale up the LAL process.

High welding speeds above 8 m/min during laser beam welding of high-alloy steel (AISI 304) lead to spatter formation, resulting in material losses and adhering spatter that significantly degrade seam quality. This effect can be reduced by using a superposition of a main intensity with a second intensity, which increases the melt pool size and decreases melt velocities. To identify the fundamental mechanism of spatter formation, high-speed synchrotron X-ray imaging was utilized to visualize keyhole behavior and the melt flow characteristics using tungsten carbide particle tracking. The addition of the second intensity increases the keyhole geometry and forms a bulge on the rear wall of the keyhole. It also reduces the upward-directed melt flow at the keyhole rear wall and surrounding the keyhole. Thereby minimizing the melt´s kinetic energy and finally, reducing spatter formation.

Monitoring the deep penetration laser welding process is relevant in order to detect deviations in the process and to achieve defect-free welds. This study aims to investigate the influence of the capillary shape on monitoring signals, as the shape and stability of the capillary have a significant effect on both defect formation and the monitoring signals.

X-ray imaging was employed to capture the capillary shape during welding. Simultaneous measurements of the back-reflected laser beam, the thermal emissions as well as depth measurements using optical coherence tomography were conducted. The simultaneous acquisition enables a direct comparison of the monitoring signals with the capillary shapes. Ray tracing simulations were performed to investigate the impact of changes in the capillary shape on the monitoring signals. The comparison between simulated and measured monitoring signals contribute to the advancement of monitoring methods in laser welding based on optical information from the process.

During deep penetration laser welding, a plume of hot metal vapor and particles is emitted from the keyhole, interacting with the incident laser beam through scattering, absorption, and phase front deformation. These interactions affect the caustic of the laser beam, potentially deteriorating weld quality. We present results from a single-shot caustic measurement of a probe laser beam, aligned coaxially with the processing laser beam. This in-situ measurement enables real-time quantification of variations in process-critical beam parameters, including pointing instabilities, focus shifts, and changes in beam quality. By analyzing the mechanisms of interaction between the laser beam and the vapor plume, our findings offer deeper insights into the interdependence of vapor plume dynamics and welding capillary fluctuations, thus advancing the understanding of laser welding processes.

The continuous joining in the rolling gap is used for thin-walled metallic bipolar plates. This development enables high production rates for cost-effective manufacturing. In a new joining process, flexible bipolar half-shells are fed into a rolling gap for welding and bonded in a second step. The challenge arises from the necessary coordination and synchronization of the multiple laser beams and the strip, with feed rates of up to 30 m∙min⁻¹. For this purpose, a multi-beam scanning optic was developed to realize partially complex weld connections using up to four fiber lasers in the flow field and the ports. Sealing is achieved through adhesive bonding in a following process. This joining technology offers advantages over laser remote welding, as significantly less energy is introduced, distortion is minimized, and coated surfaces can be preserved.

Lack of fusion defects, which result from incomplete melting in laser beam welding, present significant challenges specifically for precise applications such as fuel cell manufacturing. These defects compromise weld quality and performance, especially when producing bipolar plates made from austenitic steel. Despite extensive research into thermal, mechanical, and metallurgical factors, a complete understanding of the formation mechanism of hidden lack of fusion defects is still lacking. This review aims to describe these mechanisms by integrating experimental and computational methods such as finite element method (FEM), computational fluid dynamics (CFD), and multi-physics models to understand and mitigate defects. The findings support the development of adaptive real-time control systems and advanced models, enhancing knowledge and skills in addressing the lack of fusion defects in laser welding of austenitic steel.

Tier-1 semiconductor advanced packaging can integrate different types of chips (logic, analog, RF, etc.) interconnected on a shared interposer substrate to achieve high performance without needing monolithic dies. Glass interposers specifically offer crucial physical, electrical, chemical and thermal stability at low cost. Recently market interest has emerged for low-tier manufacturing of customised interposers for high-value, low-volume applications.

This paper discusses advantages and limitations between three different femtosecond laser drilling techniques on 0.3mm thick borofloat33 glass based on 1030nm amplifiers (fibre and solid-state): (i) single-mode percussion or trepanning laser drilling, (ii) percussion GHz-burst drilling and (iii) selective laser-assisted chemical etching. All three techniques find valuable niches for TGV sizes ranging 20-100μm depending on throughput and quality requirements. High power laser drilling rates contrast both, thermal stress management in glass, crucial for achieving high TGV areal density, and post-process surface quality to allow subsequent smooth via filling and RDL metal deposition.

The increasing demand for miniaturized and high-performance consumer electronics has driven advancements in packaging solutions, including the transition to glass interposers. A critical aspect of this development is the fabrication of high-density through-glass vias (TGVs). This study presents the formation of TGVs in various glass substrates using a femtosecond laser FemtoLux 30 operating in MHz/GHz burst modes. By employing burst mode and micromachining methods such as bottom-up milling, TGVs with aspect ratios exceeding 1:80 were achieved, with drilling times as low as 350 ms. The findings demonstrate the potential of GHz burst femtosecond lasers as a high-throughput, precise solution for TGV fabrication.

Through-Glass Vias (TGVs) are crucial for modern microelectronics packaging, enabling high-density interconnections in high power/frequency electronics as well as devices like smartphones, automotive sensors, and Micro-Electro-Mechanical Systems (MEMS). By producing vertical electrical connections through glass substrates, TGVs support device miniaturization and enhanced electronic performance. Femtosecond laser pulses are used to drill glass with minimal thermal effects, though thousands of pulses may be required for well-defined TGVs, driving demand for more efficient methods.

This study compares two approaches for producing TGVs. The ablation-based method splits a single pulse into sub-pulses with 400 ps temporal separation (GHz mode) to drill glass. The second method, selective laser etching (SLE), focuses laser pulses within transparent materials, creating etchable modified areas in aqueous solutions like KOH. Both methods outperform conventional single-pulse micromachining, achieving deeper channels and increased efficiency. These techniques hold potential for applications in advanced optics, biomedical devices, and more.

Ultrafast lasers proved to be a handy tool for the microprocessing of glass. Near-IR and visible wavelengths are commonly used for cutting, drilling, structuring, and complex-shape surface machining. Although ultrafast deep-UV lasers (usually achievable through fourth-harmonics conversion) have been available for some time, their practical use for processing is rarely reported. The main benefits of shorter wavelengths are mainly tighter focal spots and better laser absorption in the material. We present a study of the microprocessing of fused silica using a 258nm 1ps laser in combination with a galvoscanner and F-theta lens. The main aim is finding suitable parameters considering resulting roughness and material removal rate. The results are compared to similar processing using fundamental and second-harmonic wavelengths presented in the past.

We present a study on the modifications induced in fused silica by a femtosecond laser shaped into a Bessel beam, comparing three operation modes: single-pulse, MHz-burst, and GHz-burst regimes. In both the single-pulse and MHz-burst modes, the laser forms elongated, slightly tapered structures within the glass. Post-etching with Potassium Hydroxide reveals high etching rates and selectivity, reaching up to 606 μm/h and 2103:1 in the single-pulse mode, and up to 322 μm/h and 2230:1 in the MHz-burst mode. Remarkably, the GHz-burst regime enables the direct formation of taper-free holes using a single burst of 50 pulses, without any-etching. This breakthrough demonstrates the potential for chemical-free, high-speed drilling of high aspect-ratio holes in glass, opening new possibilities for advanced glass processing techniques.

An advanced laser-based method for form correction of optical elements, known as Laser Beam Figuring (LBF), is being developed by the authors. This technique intends the precise and cost-effective correction of complex surface geometries, such as aspheres and freeform surfaces. LBF allows for selective material removal from fused silica surfaces at the nanometer scale with a removal rate of several mm³ per hour, aiming for a form accuracy of less than 50 nm. Unlike traditional methods, LBF does not require polishing agents, thereby avoiding surface contamination. Additionally, LBF reduces mid-spatial frequency errors (MSFE), bridging an economic and technological gap for spatial wavelengths ranging from 100 µm to 3000 µm. The simplified equipment technology of LBF leads to savings in costs, energy, and resources, making this method an attractive alternative for the precise form correction of optical elements. In the presentation the state of the development will be presented.

Recently, there has been a trend to use diode lasers emitting in the near infrared spectral range instead of the more common CO2 lasers for powder bed fusion of polymers. However, it is important to note that melting of polymer powders with a diode laser typically necessitates the incorporation of additional optical absorbers. The majority of publications have focused on the effects of these absorbers only on the most common polymer utilized in powder bed fusion, namely polyamide. By contrast, this study analyses the absorption and resulting geometry of thermoplastic polyurethane coated with CuS nanoparticles produced by high power laser fragmentation. Monolayer samples were prepared via powder bed fusion at specific energy densities using an 808 nm diode laser setup and the resulting geometry was measured. The results show that CuS nanoparticles could be used as a suitable optical absorber in near infared powder bed fusion.

Laser-based additive manufacturing with diode lasers offers energy efficiency and compact system design but requires powders that absorb near-infrared light. This study explores how the placement of light-absorbing nanoparticles—either embedded in the polymer or attached to its surface—affects processability and part quality.

Surface-modified powders, despite ten times lower absorbance, achieved comparable melting with only 1.5 times higher laser energy. Resulting parts showed increased tensile strength without loss of ductility. Microscopy revealed that surface-localized heating preserves semi-crystalline regions, indicating a distinct melting mechanism compared to embedded absorbers. These crystalline domains likely reinforce the polymer matrix and contribute to improved mechanical properties. The findings highlight that not only the choice, but also the location of absorbers critically influences energy input and performance.

Surface modification, therefore, presents a scalable strategy to tailor powders for diode laser processing—offering new opportunities for efficient, precise, and application-driven polymer printing.

The moon serves as a steppingstone for humanity’s space colonization. Due to high transportation costs, utilizing lunar resources is considered essential for further development in space applications. Lunar regolith and its simulants exhibit a wide range of particle size distributions (PSDs). Simulants prepared under terrestrial conditions retain moisture, requiring pre-drying. Within this work, the influence of these characteristics on the melting process similar to a powder bed fusion process has been investigated.

Simulant powders of different PSDs (particle sizes ≤ 1000 µm) and drying states (undried, 300 °C and 800 °C for 4 h) were processed in a vacuum chamber and the fabricated samples profoundly analyzed. The results show an increase in sample mass with larger particles and higher drying temperatures. No correlation of the PSD and drying temperature on the porosity was observed. Processing undried simulants caused the formation of discontinuous melt tracks and a significant chamber pressure increase.

Laser-based powder bed fusion (PBF-LB/M) of magnesium WE43 shows great potential for lightweight applications due to its low density and high specific strength. Especially complex magnesium structures such as gyroid lattices with a high surface-to-volume ratio are desirable for further weight reduction. However, rapid corrosion is impeding the transfer into industrial applications.

To enhance the corrosion resistance of additively manufactured WE43, a ceramic surface modification by plasma electrolytic oxidation (PEO) has been investigated in previous baseline studies. This contribution addresses PEO of filigree WE43 structures and the evaluation of geometrical requirements like the minimal feature size. Moreover, the microstructure and corrosion resistance of the manufactured parts have been analyzed. In thin-walled specimens as well as gyroid structures, wall sizes down to 150 µm could be manufactured and successfully modified by PEO. In corrosion tests, the untreated specimen dissolved after 12 hours, whereas the modified specimen showed no signs of corrosion.

We report on a study of different hot isostatic pressing (HIP) cycles, improving the mechanical properties of additively manufactured Inconel 718 components. For this, PBF-LB/M built components are post-processed by different HIP-sequences, as gas pressure and processing time are varied, leading to differences in microstructure and material characteristics. Static and dynamic mechanical testing is performed, evaluating the changes in mechanical properties with the ultimate tensile strength and the endurance limit. Furthermore, metallographic analysis is used to investigate the achieved density and microhardness, as thermal post processing, especially HIP, leads to a significant improvement in material characteristics. Microstructural analysis, showing the grain boundaries, is used to define generated phases and precipitations of the material matrix. Moreover, the fracture behaviour is classified by grain deformation during mechanical testing, as differences in microstructure lead to highly different fatigue behaviour.

As lattice structures in various designs are used in additive manufacturing for lightweight components, the mechanical characterisation and fracture behaviour is of upmost importance for the industrial application. In this study, the fatigue behaviour of Inconel 718 lattice structures is evaluated, comparing sole PBF-LB/M to a hybrid additive manufacturing process combining PBF-LB/M with in-situ high-speed milling. At first, the static and dynamic mechanical load behaviour of different packing densities is analysed, determining the compressive strength and the endurance limit. Secondly, such hybrid additive manufactured components are compared to PBF-LB/M built parts with respect to these mechanical properties, revealing improved compressive properties and modified regimes of fatigue. In addition, differences in fracture behaviour are qualified by fractographic and surface analysis. Overall, it can be summarized that the mechanical load characteristics, especially the fatigue behaviour, are improved for hybrid additively manufactured components with a superior surface quality of Ra < 2 µm.

Laser welding has become an increasingly popular substitute for traditional arc welding over the past two decades, due to its versatility, enhanced process speed, and minimized heat-affected zone. However, many industries, such as civil, naval, or heavy-duty machinery, must conduct extensive testing campaigns to incorporate this new technology. Experimental campaigns demand many resources for each parameter variation, hindering their economic feasibility, especially for components and structures of high-added value. As an alternative, numerical simulations provide a virtual framework for analyzing welding processes, enabling the evaluation of the effects of various process parameters on the resulting structures. In this study, a finite element thermo-mechanical model is developed using ANSYS to investigate and compare diverse welding configurations and parameters. The study focuses on butt-welded S275JR steel plates using ER70S-6 filler wire. Key findings include the extent of the heat-affected zone and its implications for distortions and residual stress distributions.

Extruded recycled 6060 aluminium alloys are highly susceptible to hot cracking during laser welding due to their thermal and mechanical properties. This study focuses on developing a thermo-mechanical model to predict crack formation during laser welding of recycled AA6060 alloys with varying Cu content. A finite element model was developed, incorporating a parametrised adjustable ring-mode heat source to simulate transient temperature fields and thermal stresses.

To evaluate crack susceptibility, welds were simulated with varying edge distances to alter thermal stress and temperature distribution. Based on the thermal and mechanical behaviour of the weld pool and heat-affected zone, a stress-based index is being developed to quantify the risk of crack formation. This model aims to provide insights into optimizing welding parameters, offering practical guidance for industries such as automotive and aerospace manufacturing.

Recent advancements in dynamic beam shaping have shown the potential to revolutionise the welding process. Although this is a very attractive proposition, knowledge about the temporal and spatial response of the process to dynamic beam shaping is yet required. This study implements a multi-kW CW laser with a coherent beam combiner (CBC) and optical phased array (OPA) to modulate the fluence distribution at the microsecond scale. It investigates solidification cracking susceptibility using individual free-form beam profiles generated in the kHz regime and sequences of beam profiles switched at the microsecond time scale. A self-restraint cantilever hot cracking test was conducted on AA6082 1.5 mm sheets with full-penetration single bead-on-plate welds. Metallography analysis with electron backscatter diffraction (EBSD) was employed to correlate material microstructure with the tested beam shapes. The results are presented to highlight the unique features of modulated fluence distribution as well as current challenges and new research avenues.

High-strength aluminum alloys offer excellent weight-specific mechanical properties, making them an ideal choice for parts in electromobility applications like battery trays. However, their susceptibility to transverse hot cracking during laser welding at high welding velocities is challenging. This study investigates the mechanisms of transverse hot crack formation by means of numerical simulations of the temperature field and melt flow in the melt pool and validates the results with experiments. The results reveal a critical zone at the side of the melt pool which is characterized by a high static pressure drop at the liquidus isotherm as a result of high melt flow velocities and cooling rates, which affect the intergranular melt flow during solidification. The study provides valuable findings, which enable the optimization of high-speed laser welding of aluminum alloys, to avoid the formation of transverse hot cracks.

Aluminium alloys of the 7xxx series are renowned for their exceptional strength due to Mg and Zn precipitations. However, the presence of these precipitations reduces the ductility and thus the formability of these alloys, hindering their application for shaping operations e.g. in the automotive sector. One promising approach to improve the formability of this material class is by selectively evaporating these precipitation-promoting elements exploiting their lower evaporation temperature compared to the aluminium matrix. A spatially resolved evaporation can be achieved by localised laser remelting.

In this work, we present results on the selective element evaporation for AA7075. Key characteristics for describing the process are the evaporated amount of elements, the evaporation depth and gradients along z-direction. Cross-sections are analysed using EDX to determine the elemental distribution. Finally, element evaporation is correlated with melt pool size and the applied processing strategy to assess the potentials of a specific laser process.

With increasing competition in the EV market, reducing costs and improving thermal management in battery cases became critical for sustainable growth. This study investigated a multi-materials integration via laser welding. To achieve the dissimilar materials joining, the aluminum surface was coated using a pure Fe powder cold-sprayed processing. Disk laser welding was performed to join the dissimilar materials. The laser processing was recorded using a CCD, IR camera. This data was used to develop a CNN model to classify weld penetration depth. Mechanical, microstructural, and corrosion characteristics were analyzed. Depending on the welding parameters, the mechanical properties of the joint and intermetallic compound formation varied. However, the variation in mechanical properties was not significant because the fracture path progressed through the cold-sprayed layer. The fracture path was only influenced on penetration depth.

High-quality and efficient cavity milling of tens of microns depth is challenging and highly relevant in industrial applications. In this work, we use an innovative compact femtosecond GHz burst laser (1030nm, 800fs, burst energy >1mJ) for cavity milling of different metals. We perform engravings at different depths (30-100µm), systematically varying the burst parameters (number of pulses and burst frequency) and analyzing the ablation efficiency and quality as the engraving depth increases. We also characterized the morphology of the engraving (e.g. edge recast and bottom cavity roughness) across different laser settings, to ensure an optimal balance between efficiency, quality and depth. Finally, we optimize the post-milling processes, such as polishing and whitening. We demonstrate that by optimizing burst parameters, it is possible to achieve efficient and high-quality milling at various depths. Furthermore, an optimized initial engraving strategy is essential for obtaining high-quality surface finishing, even at the highest depths achieved.

High precision micro-drills with solid Polycrystalline Diamond (PCD) sintered onto Tungsten Carbide (WC) shanks are crucial for machining electronics components. These drills consist of multiple complex geometrical features that are difficult to machine into small shank diameters bits using traditional manufacturing methods. A multi-laser approach, employing two laser systems, a nanosecond water jet guided (WJG) system and a nanosecond galvo scanner-based system, was used to produce the PCD twist micro-drills. This main study focuses on finding the optimised laser and kinematic parameters for WJG laser turning of WC shanks and the nanosecond machining (roughing and finishing) PCD flutes and cutting edges. The study also includes investigating laser-material interaction phenomena to ensure ideal microstructure, geometric, and surface quality of the PCD micro-drills. This multi-laser approach produced micro-drills with improved geometries and sharper cutting edges, which is expected to extend the service life and enhance the machining quality of the PCD micro-drills

The CEA (Commissariat à l'énergie atomique) is a French government-funded research organization that conducts a wide range of research. One of the facilities operated by the CEA is the Laser Mégajoule (LMJ), which is used for high power laser experiments. These experiments are used to study various physics phenomena, including fusion reactions, which require small plastic capsules filled with high-pressure deuterium. The CEA is responsible for designing, studying, and manufacturing these targets for the experiments.

This talk explores the development of a drilling process using a Ti:Sa femtosecond laser. Various procedures and optical configurations have been tested to create accurate and reproducible conical hole shapes. A robust and versatile process has been established, resulting in outer diameters ranging from 8 µm to 38 µm and inner diameters from 6 µm to 18 µm, through capsule walls as thin as 100 µm.

This study investigates the use of femtosecond laser processing to optimize cutting tools, specifically a V-shaped point tools made from ultra-fine (UF) grain carbide with an 8 mm diameter. The process involves optimizing edge geometry and creating surface textures that enhance lubricant retention. Femtosecond lasers offer high precision, enabling chamfering of cutting edges to improve tool performance, durability, and material removal. Surface texturing reduces friction, improves chip evacuation, and promotes better lubrication. Key applications include drills, end mills for hard materials, and specialized tools used in medical and aerospace fields, benefiting from customized textures and geometries.

In this work, cutting edges are modified with 14 µm and 20 µm chamfers to enhance durability. The cutting edge margin is textured with dimples 1.6 µm-deep and 16.5 µm-diameter to ensure superior lubricant retention and reduce friction during machining. These findings demonstrate the potential of femtosecond laser processing for effective industrial tool optimization.

The feedstock in laser beam powder bed fusion of polymers (PBF-LB/P) is limited to a few materials with strict flowability requirements, compromising its economic efficiency and sustainability. A general route to nanoadditivate polymer powders for PBF-LB/P to tailor the polymer properties will be presented. The process employs laser produced nanoparticles that are directly adsorbed on the polymer powder, followed by drying, analysis and PBF-LB/P processing. The homogeneously dispersed nanoparticles on the polymer powder transfer their plasmonic or magnetic properties to the produced polymer parts with a nanoparticle loading below 0.1 wt%. To further reduce the required nanoparticle loading, electrophotographic powder application (EPA) is employed during PBF-LB/P, coating the parts with only two Ag-PA 12 layers and showing S. aureus and E. coli bacteria growth inhibition. The proposed approach can facilitate polymer powder functionalization and selective surface modification towards graded materials printing at reduced cost and waste generation.

Increasing electrification imposes challenging requirements on power electronics. These power electronics feature small functional structures, which are preferably made of pure copper and are built on sensitive ceramic-based substrates, so called Direct Bonded Copper (DBC) substrates. An innovative additive manufacturing (AM) approach employs the laser powder bed fusion (PBF-LB/M) process to manufacture the functional structures directly onto the DBC, enabling the reduction of manufacturing cost and effort. Processing of pure copper in the PBF-LB/M process is challenging due to its reflectivity and its thermal conductivity. Additionally, using a DBC in the PBF-LB/M process causes complex multi-material interactions. Focusing on the application, the processability of pure copper with a green and an infrared laser in the same machine setup was investigated. The influence of laser wavelength and process parameters on the resulting part properties was analyzed, differences between both wavelengths were pinpointed, and suitable parameter sets were identified.

Additive manufacturing offers great potential in the aircraft sector due to its high degree of design freedom and new material developments such as Scalmalloy®, a light aluminum alloy with high mechanical properties. Related works show a lack of knowledge about the additive manufacturing of Scalmalloy, so this paper aims to identify optimal process parameters. A design of experiment is performed and the hardness, tensile strength, and surface roughness are measured. After that, dimensional design parameters are investigated. With the optimized process parameters, a density of 99.87 % is achieved. The hardness is 168.5 HV0.3 and the tensile strength is 541.7 MPa after thermal treatment. Surface roughnesses between 41 and 20 Ra are measured depending on the build direction. Minimum manufacturable dimensions are defined for walls, cylinders, and inclination angles. The identified process parameters and the characterization of mechanical properties deliver fundamental knowledge to make Scalmalloy® usable for aircraft applications.

The surface quality of metal parts manufactured by laser assisted powder bed fusion varies significantly. To understand the surface formation process it is critical to understand the sintering/melting dynamics of particles. However, it is usually not possible to observe heating, melting and resolidification during the additive manufacturing process.

We present a setup that enables the in-situ optical and thermal imaging of the laser-initiated melting and the solidification of micrometer sized metal powder particles. The system consists of an optical tweezers setup that allows both a precise positioning of single particles as well as the melting of the particles using a ultrashort pulsed laser system operating at a wavelength of about 1.3 µm. Combining high-speed imaging offering a spatial resolution of 0.6 µm and a framerate up to 1,100,000 fps together with a micro-thermography system detecting spectral information between 2 µm and 5.5 µm the temperature dependent flow mechanics are measured.

Detailed knowledge about the physics of the PBF-LB/M process is still lacking, and the simulation of the fast and small-scale process is challenging. Especially the experimental validation of complex simulations lacks a suitable measurement technique for temperature distributions at high speeds and spatial resolution. The complicated process physics, specifically the rapidly changing emissivity in and around the meltpool, pose a severe challenge for usual thermographic approaches.

Here, we present first results of a hyperspectral measurement approach to reconstruct temperature and emissivity maps during the PBF-LB/M process in a custom manufacturing machine. The camera setup measures the thermal radiation of the process along a line at a rate of 20 kHz, spectrally resolved between 1 µm and 1.6 µm. When the meltpool travels perpendicularly across this line, a typical meltpool can be reconstructed by pointwise fitting for temperature emissivity separation, based on typical spectral emissivities from reference measurements.

Hairpin winding technology is essential in electric drives for traction applications. This process involves inserting copper bar segments coated with an insulating layer, cut, and bent to shape. Laser welding is used to connect the hairpins at the final production stage, which depends heavily on enamel stripping quality. Residual enamel can cause weld defects, while over-stripping leads to conductivity damages. Hairpin stripping can be achieved via lasers, offering flexibility in size and geometry, or cutting tools, which involve simpler machinery. Each method differs in material removal, resource use, waste generation, and defect potential. However, the benefits and limitations of digital laser technology over the mechanical milling process require further evaluation and objective measures. This study systematically compares laser removal and milling for hairpin stripping, analyzing productivity, defect types, joint strength, and electrical conductivity. It benchmarks the two methods based on resource efficiency and waste generation.

A novel hybrid welding method combines laser and MIG welding for enhanced performance. A narrow gap is created between the workpieces, and a laser head with an oscillating beam is positioned alongside a MIG torch. The laser preheats the workpiece edges and partially heats up the melt pool formed by the MIG process. The melt fills the entire gap. This dual role of the laser improves weldability, surface wettability, and melt flow characteristics. The metallurgy of the weld can be tuned using the composition of the filler wire. Therefore, this method is also suitable for dissimilar welds with appropriate filler wire. Consequently, the method yields superior weld quality across the entire cross-section with improved uniformity in chemical composition, geometry, and microstructure. The method is currently under investigation for various steel grades, including structural and austenitic stainless steels, and their combinations.

In recent years, special steels have attracted considerable interest due to their high strength, wear resistance and weight reduction potential. However, the industrial application of high carbon steels remains limited because of their challenging weldability. This study investigates the use of laser preheating before welding and laser heat treatment after welding to enhance the mechanical properties of high carbon steels. Unlike traditional methods such as furnace or induction heating, a novel approach utilizing an oscillating laser welding head was successfully implemented, allowing localized heat treatment application. The process was optimized for a specific weld length by adjusting the number of heating cycles and laser power. Mechanical tests revealed significant improvements in strength and hardness for materials that are otherwise completely unsuitable for welding without heat treatment. The results show the potential to open up wider industrial applications for the welded use of high carbon steels.

With new opportunities for processing, recycling and repair, thermoplastic carbon fiber-reinforced polymers (TCFRPs) offer promising approaches to tackle the economical and sustainability challenges of tomorrow’s aviation industry. The authors enabled the manufacturing of the longitudinal butt joint of the world’s largest thermoplastic aircraft structure: The Multifunctional Fuselage Demonstrator (MFFD), created in the European Union’s Clean Sky 2 project. Using a CO2 laser source, fully-consolidated multidirectionally reinforced TCFRP laminates with 6 plies were welded onto the longitudinal butt joint in a one-shot process. During welding, multiple parameters were adjusted constantly to achieve a joint with high homogeneity, such as laser power, beam shaping and feed rate. Mechanical testing (ILSS) has shown that the produced joints offer similar strengths as reference samples from conventional heat press co-consolidation, without any post-processing necessary after the layup of the laminates.

Hybrid polymer-metal parts gain popularity in industrial applications, for example for lightweight structures or parts with combined material properties. In order to join metals and plastics laser direct joining is often the process of choice, leading to strong and reliable joints without adhesives, primers or mechanical fasteners and can therefore also be used in medical technology. Laser direct joining of metals and polymers is based on two processes. To achieve a good mechanical bond between the parts, the surface of the metal part is structured in a first step. In the second step, the polymer is heated in order to allow the melt to flow into the prepared metal structures. When using highly filled, fiber-reinforced high-performance polymers, which are required in many demanding applications, melt flow into these structures can be hindered. Process optimizations are presented to avoid air enclosures in the structures, surface defects or inhomogeneous bond properties.

Multi-materials which can save weight are important materials to realize carbon neutrality. Our innovative laser direct joining method is effective for joining different materials such as difficult-to-join composite materials and light metals. However, its joining mechanism and properties have not been clarified so far. Therefore, the objectives of this research are to clarify the joining mechanism of laser direct joining of difficult-to-join composite materials and light metals by integrating cutting-edge observation and analysis with materials informatics (MI) and computational science, and to control the dominant factors of joining by optimization of surface modification, etc. to realize ultimate joining strength, superior reliability and environmental durability that can be used in space and deep sea.

In laser micromachining, the complex and non-linear laser-matter interaction prevents theoretical models from predicting optimal engraving parameters to meet time and quality criteria, often requiring numerous experimental tests for each new process to be developed. These traditional approaches are resource-intensive, requiring substantial machine and personnel time. To address these challenges, we propose an innovative methodology leveraging artificial intelligence (AI) to streamline the parameter optimization process. By combining a robust experimental database with advanced AI techniques, such as machine learning models and optimization algorithms, our approach enables the prediction of optimal laser parameters to meet dimensional and quality criteria without relying on exhaustive empirical testing for each new process.

Our latest results on this methodology will be presented, demonstrating its capacity to predict key parameters such as energy per pulse, speed, frequency, and pitch. This approach reduces resource consumption and accelerates process development, offering a transformative step forward in the field.

This research focuses on using femtosecond laser pulses for polymer cutting process optimization. Since polymers consist of very large molecules and are sensitive to heat, utilizing ultrashort pulse lasers can significantly expand their application potential in biomedical, micro-optics, and electronics fields. Polymers are getting more and more attention as a versatile material for biomedical, micro-optics and other applications where specific polymer properties are needed. During polymer cutting with femtosecond laser pulses better quality can be achieved avoiding heat affected zones (HAZ) due to indirect lattice heating, thus benefiting from “cold” ablation. We demonstrate cutting various thickness polyamide (PI), polyethylene (PET) and polycarbonate (PC) films. During experiments laser parameters such as pulse repetition rate, average power and pulse overlap were optimized to achieve high-quality efficient cuts and avoid HAZ. As a result, process parameters were optimized for each polymer cutting with ultrashort pulse laser.

This study investigates the behavior of three commercial polymers under high repetition rate (1 kHz–1 MHz), femtosecond (450 fs) laser irradiation at 1030 nm, 515 nm, and 343 nm, using different combinations of pulse numbers (100–400) and fluences (0.91–1.68 J/cm²). The influence of repetition rate and wavelength on ablation morphology is evaluated. At MHz repetition rates, larger ablation volumes and reduced thermal effects are observed. To interpret this behavior, we develop a simplified thermal diffusion model to estimate heat accumulation between pulses. The results suggest that, in the sub-MHz regime, heat removal by thermal decomposition dominates over diffusion losses, reducing average temperature rise — a behavior consistent with ablation cooling. This interpretation is supported by morphological measurements, indicating reduced thermal modifications at higher repetition rates. Observing ablation cooling below the GHz regime enables its analysis without shielding effects interference, providing insights into underlying heat diffusion mechanisms.

Solar cell production is entering the terawatt range. With laser- processing being an important part of silicon solar cell manufacturing, a laser tool is required to reach a throughput of over 10,000 wafers per hour (wph) with accuracies of 10-100 µm and small structure sizes (<30µm) over the full solar cell area.

To meet these demanding requirements, we have developed a new laser machine concept relying on on-the-fly processing and integrated tracking.

Velocity fluctuations on high-throughput conveyor belts are measured using custom optical tracking hardware, enabling real-time active oscillation compensation through synchronization with the laser scanner. With this approach the pattern oscillations through transport imperfections could be reduced from 82.2µm to 13.2µm (1σ).

To meet the necessary beam velocity of 1km/s and numerical aperture, polygon scanners are demonstrated to be well suited in combination with this on-the-fly processing approach, reaching a processing time of just 200ms for a full wafer.

Ultra-short pulse lasers open up new possibilities in the development of laser manufacturing processes with an extreme control of surface properties. For this reason, they have been introduced in several processes applied to damage-sensitive materials. This requires the introduction of monitoring technologies for the in-operando detection of phenomena occurring during the irradiation process. The latter can significantly affect the quality of the desired end result. This work presents acoustic monitoring as a powerful tool in several areas. These include the development of laser cleaning protocols for the preservation-restoration of stained glass in Cultural Heritage, the control of wettability in wind turbine blade surfaces, or the implementation of micromachining processes on ceramics and transparent conductive oxides with applications in the energy sector. An adequate analysis of the sound signal facilitates the selection of the most appropriate processing conditions and can also be used to evaluate the results of the laser treatment.

Tangential femtosecond laser micromachining is a modern technique suitable especially for machining hard materials with high precision in the manufacturing of rotary workpieces in a tangential position (laser turning). This study investigates the use of tungsten carbide rods with cobalt binder as a base material. Two machining strategies were tested: standard and adaptive. A closed-loop system combining a camera and software was used to monitor and control the process. The adaptive approach adjusted the laser path in real time to maintain the optimum angle of incidence (AOI) according to the changing geometry of the workpiece. The main objective of the research was to evaluate how AOI control affects material removal rate (MRR) against the standard approach. The results showed that adaptive control significantly increases MRR and process efficiency. These findings contribute to the development of tangential femtosecond laser micromachining for industrial applications requiring high-precision production of hard materials.

Ring beam shaping represents an innovative approach and a promising technique in Laser Powder Bed Fusion of metals (L-PBF/M). Due to its energy density distribution, it is capable to produce wider melt tracks, reducing the thermal gradients and enhancing process stability compared to traditional Gaussian beams.

This study aims to evaluate the effectiveness of using a ring-beam shape in L-PBF/M fabrication of Ti-6Al-4V components, by investigating its impact on temperature distribution, microstructural characteristics and residual stresses. Specifically, a coaxial dual-wavelength pyrometer has been employed to capture temperature data during fabrication, generating a heatmap of the process, while residual stress measurements have been conducted using the contour method and X-ray diffraction. The cooling rates have been also evaluated and correlated to the microstructural features and residual stresses.

Laser Powder Bed Fusion (L-PBF) enables precise fabrication of complex metal parts but is limited by slow build rates. Increasing laser power can help, but conventional Gaussian beams at high power cause excessive evaporation and spattering, leading to defects.

Defocusing reduces peak intensity but is limited by Rayleigh length and thermo-optical effects. Beam shaping offers a more effective solution, achievable through dual-core lasers or external optics like Multi-Plane Light Conversion (MPLC) technology, which enables adaptable beam profiles such as annular or M-shaped distributions.

This study applies beam shaping to high-power laser printing of nickel alloy 625, achieving a 3.3× speed increase while maintaining part quality. Mechanical testing, high-speed imaging, and particle tracing confirm the benefits of shaped beams over standard Gaussian profiles.

We will also discuss latest implementation including fast switch in between a shaped beam and the initial Gaussian.

Powder Bed Fusion of Metals with Laser Beam (PBF-LB/M) offers considerable potential for the fabrication of performance-enhancing soft magnetic components with high topology freedom for electrical machines. FeSi6.5 soft magnetic iron-silicon alloy is a pivotal component in multi-material soft magnets, owing to its high electrical resistivity and low magnetic losses. However, the high silicon content of 6.5 wt.% leads to inherent material brittleness, which presents several PBF-LB/M challenges. Rapid melting and solidification generate steep thermal gradients that cause significant stresses and associated cracks in the less ductile FeSi6.5 material. This effect is exacerbated in the case of a Gaussian energy distribution with extremely high local temperatures in the laser beam center. In this work, laser beam shaping with ring-core energy distribution for PBF-LB/M of FeSi6.5 to suppress cracking without additional heating is investigated. Correlations between Gaussian and ring-core energy distribution and their effect on component properties are analyzed and discussed.

Permanent magnets are essential in electric power generation, electromobility, and robotics applications. However, the high cost and limited availability of the required rare-earth (RE) elements pose a significant challenge. Therefore, laser powder bed fusion (PBF-LB) as a method to produce permanent magnets with near-net shapes provides new possibilities to optimize RE material consumption. However, a common limit of PBF-LB is the low coercivity of as-built parts, which arises from microstructural defects such as grain growth, oxidation, and poor alignment of magnetic domains caused by processing. To overcome this, we investigated the combined effects of process parameters and the surface modification with nanoparticles of Nd-Fe-B-based micropower feedstocks. Our results demonstrate that nanoparticles enhance solidification, leading to increased part density and coercivity. These findings provide valuable insights into optimizing rare-earth-based feedstocks for PBF-LB, enabling more sustainable and efficient production of high-performance permanent magnets.

THz metamaterials offer opportunities to address the "THz gap" caused by the weak electromagnetic response of natural materials in this frequency range. We present a novel design of three-dimensional, metallic "cactus-like" meta-atoms that exhibit electromagnetically induced transparency (EIT) and enhanced refractive index sensitivity at low THz frequencies (1).

The fabrication process combines multiphoton polymerization with selective electroless silver plating to create conductive and mechanically intact structures. Multiphoton polymerization enables the production of intricate, sub-micron features, while selective silver plating ensures the required metallic properties for THz interactions.

Experimental characterization using THz time-domain spectroscopy (THz-TDS) confirm the metamaterial’s response. This manufacturing approach shows the potential of these structures for slow light and high-performance sensing applications.

(1) Papamakarios, S. et al. Cactus-like Metamaterial Structures for Electromagnetically Induced Transparency at THz frequencies. ACS Photonics (2024). https://doi.org:10.1021/acsphotonics.4c01179

Due to differences in absorption coefficients and melting points, direct laser welding of dissimilar metals between copper and stainless steel(SS) remains a challenging topic.In this work, we present a blue-infrared hybrid laser welding technology for efficiently joining copper to SS. By leveraging copper's high absorption of the blue laser (455nm),preheats the material、improving absorption of IR laser and reducing welding defects caused by differences in absorption and heat dissipation. The high brightness of the IR laser ensures sufficient weld depth and joint strength.

The results demonstrate improved thermal management, leading to smoother welds and a reduction in defects, such as cracks and porosity, by optimizing key process parameters, such as laser power, welding speed, and offset.

Moreover, the technology was successfully extended to weld copper up to 19mm in thickness, illustrating the robustness and versatility of the hybrid laser welding technique for producing high-quality joints in challenging applications.

In recent years, there has been a growing focus on aluminium-copper welds, as substituting copper with aluminium can significantly reduce the weight and costs of electrical systems. Laser welding has emerged as a reliable and productive technology for joining dissimilar materials. However, welding of aluminium and copper often results in the formation of brittle intermetallic-compounds (IMCs), which also can exhibit higher electric resistance. A promising approach to minimizing IMCs involves the use of laser with wavelength ranging from 445 nm to 535 nm. Given that it is a diffusion-driven process, it promotes the formation of a dominant eutectic layer in the joint over intermetallic compounds. In this study, a blue laser source is employed for spot welding of copper and aluminium. The clamping pressure is varied from 0.25 N/mm² to 2.5 N/mm². The focus is on characterisation of the eutectic layer formed from Al2Cu and α-Al, together with IMCs.

E-mobility increasingly demands cost-efficient and lightweight solutions. Although copper remains indispensable in battery production for its excellent electrical and thermal conductivity, it is increasingly replaced with aluminum to reduce weight and production costs. However, complete substitution is challenged due to issues like contact erosion during operation, necessitating reliable copper-aluminum joints. Laser welding is preferred for its high precision, deep penetration, and minimal heat-affected zones. However, a major challenge in laser welding of copper-aluminum is the formation of brittle intermetallic compounds (IMCs) at the weld interface. This study investigates IMC formation mechanisms and the influence of cooling rates on their behavior in two laser welding processes: conventional and indirect laser welding. Indirect laser welding has recently been developed as a solid-state process to minimize material mixing and IMC formation, typical of fusion welding processes. This study includes a comparative analysis of the welding interface in both processes.

During fusion welding processes shielding gases are of major importance to protect the liquid metal from atmospheric contamination. These shielding gases play an important role in a number of aspects of welding, including the overall shape and microstructure of the weld, imperfections and the formation of weld bead and root. The aim of this work is to present the potential of an innovative and patented shielding gas nozzle which generates a spiral high-speed gas flow around the fusion zone and thus provides unidirectional welding conditions even at high welding speed > 10 m/min. Welding tests on butt and lap joints in stainless steel 1.4404 and titanium grade 5 show advantages with regard to uniform surface of weld bead and root. Furthermore, suppression of cracking and spattering can be observed, which result from the effective displacement of atmospheric gases by the spiral-shaped shielding gas flow.

A project associated to the authors aims to demonstrate an innovative liquid hydrogen tank concept for emission-free aviation. Liquid hydrogen tanks operate under a pressure of approximately 4 bar, resulting in "boil-off" gas—hydrogen that must be vented due to thermally induced pressure increases, which reduces efficiency. To minimize this, a multilayer vacuum insulation in a sandwich structure made of additively manufactured chromium-nickel steel is being developed. The individual segments of the resulting tank must be welded together. Laser beam welding in a vacuum combines the welding process and the creation of vacuum insulation in a single step. Trials with 2 mm thick stainless steel sheets, arranged at distances of 5–20 mm and welded together, demonstrate the process feasibility. The results show a broad parameter range for three-sheet connections, enabled by both beam oscillation and Brightline technology.

The cost aspect is becoming increasingly important in the manufacturing of complex additively manufactured components. One method of reducing costs is hybrid design, i.e. combining semi-finished products with the additively manufactured components. For this reason, the focus is on welding processes to improve overall performance of the final component. Laser welding is particularly suitable for joining components to avoid subsequent processes issues such as distortion due to the low heat input.

As part of the study, the aluminum alloys AlZn5.5MgCu (EN AW-7075) and AlSi7Mg0.6 (EN AC-42200) were used to build components using L-PBF and to weld them using laser high-frequency beam oscillation. That approach enables hot-crack free weld seams and provides high process stability towards avoidance of melt pool blow-outs. The paper shows the developed process approach and resulting properties (microstructure of the weld, tensile strength and fatigue strength) were compared with alternative welding processes (FSW, EBW and GTAW).

Femtosecond lasers are increasingly used in micro-processing, particularly in the display and semiconductor industries. However, their free-space propagation makes beam shaping highly sensitive to thermal instabilities, reducing process stability.

We investigate mode-cleaning, a passive beam stabilization technique based on Multi-Plane Light Conversion (MPLC). By filtering unwanted spatial modes, mode-cleaning ensures a more stable beam profile. We explore different configurations and demonstrate its benefits for micro-processing, notably improving top-hat beam drilling stability.

Additionally, we highlight its advantages for fiber launching into hollow-core fibers, enhancing robustness and enabling industrial deployment. This breakthrough could revolutionize femtosecond laser delivery, particularly in robotic applications.

Making full use of today available femtosecond mean power without losing the high processing quality of femtosecond laser is not straightforward and require advances in beam engineering. The choice of the mean laser power is the main process parameter for improving the productivity of a considered application. This choice is nevertheless strongly corelated with the beam engineering process strategy. Of particular interest is spatial shaping, for division of the beam into multiple spots on the sample. In this work, we combined a 300 W fs laser (Tangor from Amplitude) with a Spatial Light Modulator (SLM). A line of spots, ranging from 1 to 50 was generated both in the scanning direction (“Rosary”) and perpendicular to the scanning direction (“Rake”) for a variation of the total fluence from 1 J/cm² up to 80 J/cm². The results highlight a more efficient use of the available fluence when using beam divisions.

Spatial light modulators (SLM) can accelerate ultrafast laser processes for rapid surface patterning. The technique relies on applying a phase mask with the SLM in order to generate an array of laser spots for parallel processing, or to shape the laser spot itself into a desired intensity distribution such as a top-hat, line, non-diffractive beams etc. Experimentally, the laser intensity distribution can significantly differ from the desired one, with the appearance of speckle and the stray ‘0th order’. In this contribution, we consider the main factors being at the origin of this discrenpancy, such as the SLM limited spatial resolution, quantization and aberration and quantify their effect on the beam shaping efficiency and homogeneity. By using a Fourier-based propagation code, we numerically evaluate the laser intensity distribution in the focal region. This permits to estimate in the loss of available energy for laser ablation when spatial beam shaping is employed.

Fiber-guided beam delivery has facilitated the widespread adoption of cw lasers in industrial material processing applications. Similar beam delivery solutions are now available for ultrashort pulse laser systems. Limitations of conventional solid core fibers regarding pulse energy, peak power, and dispersion can be overcome by utilizing micro-structured hollow-core fibers. Today, ultrashort pulses with pulse energies exceeding several 100 µJ and peak powers of up to 1 GW can be delivered with these fibers while maintaining excellent beam quality. Here, we report on recent advancements in our modular fiber beam delivery systems and their application in laser micromachining, including surface micro-texturing. Key aspects such as transmittable pulse energies, long-term stability, beam quality, and polarization maintaining properties during dynamic applications are discussed. These beam delivery systems serve as versatile tools for flexible laser integration and enable the commercial use of complex multi-axis manipulators and robotic arms in laser micromachining applications.

Galvanometric scanners, widely used for beam deflection in laser material processing applications such as welding, cutting, and additive manufacturing, provide precise and rapid laser focal spot positioning. However, the growing demand for reduced cycle times and improved positioning accuracy poses significant challenges to their dynamic performance. Inertia-induced discrepancies between desired and actual geometries, especially at acute angles and at high operating speeds, can negatively impact the processing outcome. This study introduces innovative trajectory planning methodologies designed to enhance scanner dynamics without requiring hardware alterations. By optimizing or pre-calculating scanner input trajectories, these approaches effectively counteract inertia-induced deviations, thereby improving geometric accuracy and processing results.

The integration of galvanometer scanners and robotic manipulators in laser material processing poses challenges due to their independent hardware and software architectures. Synchronizing these systems requires precise coordination of robotic motion and galvanometer scanner control, particularly for complex path planning tasks. This paper introduces a ROS-based framework that leverages the Robot Operating System (ROS) and its open-source, modular, and widely-adopted capabilities in robotics to unify the control of robot and galvanometer scanner. A service-oriented, publish-subscribe wrapper is developed to manage scanner mirror positions and robotic joint movements, ensuring accurate laser beam positioning and process consistency. A case study in laser marking validates the framework's functionality, highlighting its adaptability to other applications such as welding and cutting. Future research may explore additional factors such as dynamic power control, deep learning, and vision-based system integration. This scalable and flexible approach demonstrates the potential of ROS to drive innovations in laser material processing.

The integration of collaborative robots (cobots) into laser-based material processing offers significant potential for flexible and cost-efficient automation in remanufacturing, a crucial part of circular economy. Recent advances in laser technology and the adaptability of cobots make them well suited for resource-efficient processes that require precision and flexibility.

This paper presents an approach in which additional sensors are integrated into a cobot to refine part positioning after the operator has roughly learned the initial position. Based on this improved positional accuracy, the robot autonomously performs precise path planning and executes automated laser cleaning tasks. This enables the effective removal of contaminants or coatings, a common requirement in reprocessing operations.

A laser cleaning case study illustrates how sensor fusion, adaptive path optimization and offline simulation improve accuracy and streamline workflows. The results show the potential of cobots to improve precision, simplify human-robot interaction and optimize remanufacturing processes through advanced automation strategies.

Over the past several years, the University of Dayton Research Institute and the US Air Force, have been developing advanced laser (300W fs) surface processing techniques, hollow-core fiber coupling methods, and in-situ process monitoring technologies to enable robotic implementation for large-scale components.

Focusing primarily on composites to date, a body of mechanical bond-strength, thermal, and laser quality data will be discussed. These applications are enabled by the developed in-situ process monitoring and feed-forward control which allow large complex structures to be processed while remaining in focus. Data was collected to measure resultant laser beam quality of the automated system during motion to ensure process stability.

Finally, process rate and cost considerations will be discussed and how those variables impact not only the applicability of advanced laser processes to current needs, but also how these considerations may drive the direction of research and commercial laser offerings into the future.

The integration of AI methods into photonic production chains, especially when evaluating data to assess the process result, is associated with high expectations. Machine learning should not only make processes and quality information more reliable, but also provide real, tangible results, physical quantities that describe the process result in µm or µOhm or kN.

Furthermore, shaped light has been shown to play a crucial role in improving the precision and versatility of laser material processing. By adjusting the intensity distribution of the laser beam, shaped light enables a more controlled energy input and thus a larger and significantly more robust process window.

It seems clear that the combination of these two innovative approaches marks a new path in industrial laser material processing and that both have a positive influence on each other. This is particularly beneficial for demanding welds in the context of e-mobility and the specific materials used.

The framework for characterizing laser beams according to ISO 11146 gives appropriate results for Gaussian to top-hat shaped beams in their focal planes for quantities such as 2nd-order moment beam width (dσ), Rayleigh length (zR) and beam propagation factor (M2).

These quantities are not ideally suited to describe laser beams created by a range of new technologies that generate ring-shaped beams. This deficit is compounded when “mixed” beams with a central beam surrounded by a ring beam are used.

A new set of parameters to describe ring-shaped beams more adequately and with a focus on the application is presented. Both for single planes and entire beam caustics, we describe how beam features are extracted. A comparison of the new method with the ISO 11146 approach is provided, based on real world examples. The presented method can serve as a framework for a future norm on ring-beam analysis.

Laser beam welding is widely utilized across various industries, including the automotive, nuclear power plant, and petrochemical sectors, due to its excellent compatibility with remote control and automation. It enables high-quality welding with a smaller heat-affected zone compared to other welding techniques. However, during high-power laser irradiation, spatter generation commonly occurs, which contributes to defects such as weld wall thinning and porosity.　In our previous study, we determined that spatter generation is caused by fluctuations in the keyhole during laser irradiation in vacuum conditions. To address this issue, this study employed a multi-spot laser approach in laser beam keyhole welding to develop a spatter-free process, clarifying the effects of multi-spot lasers on spatter suppression.

Laser keyhole welding of dissimilar materials, such as aluminum-copper (Al-Cu) and copper-steel (Cu-1.4301), is important for joining electrical components (battery to busbar). However, the joining process remains challenging due to the narrow process window and the formation of brittle intermetallic compounds (IMCs). Beam oscillation superimposed to the weld trajectory has indicated to expand the process window by modifying heat distribution and influencing IMC formation.

This study investigates the effects of spatial and temporal beam shapes created by FlexiBeam-technology. This technology utilizes a galvo scanner for non-stationary beam shaping by means of oscillation in the kilo-Hertz regime. It generates intensity distributions, such as lines, rings, rectangles, and complex patterns (T-shape). Lap-joint configurations of Al-Cu and Cu-Steel1.4301 are analyzed to study weld intermixture and IMC formation. The results show that specific beam shapes improve process stability. They also reduce IMC growth, leading to better joint quality in dissimilar material welding.

The increasing demand for lightweight, high-strength materials has led to the widespread use of aluminum alloys, in various industries. However, welding these alloys, particularly 6082, presents challenges due to their composition, which includes magnesium and silicon. The differing melting points of these elements cause inconsistent melting and solidification, leading to issues such as porosity, cracking, and reduced strength in the heat-affected zone.

This study focuses on: BrightLine and Rotating Bifocal Optics. BrightLine offers remarkable flexibility by allowing the laser power to be directed entirely to the core fibre, the ring fibre, or distributed between both. Rotating bifocal optics using double wedges split the laser beam into two beams that rotate around a specific radius under identical parameters.

The research focuses on optimizing these techniques to improve weldability and reduce defects like cracks and porosity in 6082 aluminum alloys. Both methods were successfully optimized, achieving the desired welding results.

Highly dynamic beam shaping offers enhanced capabilities and flexibility for the optimization of laser welding processes. The application of dynamic beam shaping requires knowledge about the influence of the frequency on the resulting melt flow and melt pool geometry. In the talk, we present an analysis of the effect of highly dynamic beam deflection during welding of stainless steel and aluminum, using a numerical model and high-speed imaging. In order to determine the limits of using highly dynamic beam deflection, the welding process with a static beam shape equivalent to the average dynamic shape was investigated. The results show different regimes of the melt pool and keyhole characteristics depending on the beam deflection frequency. A significant change in melt flow and melt pool geometry was observed when the (quasi-) static limit is reached.

In order to optimize the behaviour of keyhole and melt pool during laser welding, recent beam shaping technologies allow for manipulating the intensity distribution. Dynamic beam shaping by means of coherent beam combining offers almost unlimited flexibility in changing the intensity distribution on the workpiece surface. The intensity distribution can be dynamically modulated at MHz frequencies. The effects of this fast modulation of the beam shape at previously unachievable frequency ranges has not yet been thoroughly investigated. Within the framework of this study we analyzed the frequency-dependent behaviour of the keyhole and melt pool geometry when changing beam shape periodically at different frequencies. The geometric dimensions were determined by means of Highspeed imaging and polarization goniometer. The results specify the frequency related requirements and limits in dynamic beam shaping during laser welding processes, which are of highest significance to design optimization strategies in laser welding processes.

The identification of optimal process parameters is crucial for the development of high-quality laser welding processes. A challenge in laser welding lies in the occurrence of defects such as spatter, undercuts and hot cracks, which result from instabilities in the keyhole and melt pool during the welding process. A recent study demonstrated that dynamic beam shaping using a laser based on Coherent Beam Combining can effectively stabilize the welding process, as shown for copper welding, which can contribute to an improved weld seam quality. However, determining suitable process parameters typically requires extensive and time-consuming experimental investigations, combined with process-specific expertise. In this study, Bayesian optimisation was applied to efficiently identify parameters for welding using dynamic beam shaping, achieving weld seams with defined depths and minimal defects while significantly reducing the number of required experiments, even at high welding speeds. The experiments were conducted on AW5754.

Understanding GHz surface acoustic waves (SAWs) is critical for advancing nondestructive testing and material characterization in applications like semiconductor wafers and optical crystals. Traditional SAW measurement methods often rely on time-consuming point-based techniques, requiring multiple scans to capture angularly resolved wave propagation. This study employs a fast, full-field imaging approach using ultrafast pump–probe microscopy with subpicosecond infrared laser pulses in the ablation regime. This method captures angular propagation velocities of Rayleigh SAWs and high-velocity pseudo-SAWs in fused silica and x-cut quartz. Reflectivity modulations were recorded using a high-resolution sCMOS camera, enabling an observation of wavefront dynamics over a time delay range of 6–11.5 ns. The results matched finite element simulations, achieving relative errors between 2–5%. From the measured wave velocities, key material parameters such as Young’s modulus and Poisson’s ratio were derived in excellent agreement with literature values. This technique demonstrates potential for faster, accurate material characterization.

Despite decades of research on laser-induced-periodic-surface-structures (LIPSS) establishing the role of inhomogeneous energy absorption, temperature gradients, and melt-flow dynamics, material-specific feasibility of LIPSS formation on metals remain incompletely understood. Current theories attribute differences to thermophysical properties and fluid motion, assuming universal optical mechanisms. However, we identified an overlooked factor: material-specific single-pulse morphology.

Through comparative pulse-to-pulse analysis of aluminium and stainless steel, we observed the development of LIPSS on steel, while Al developed a chaotic surface morphology regardless of the pulse number. Using near-field simulations of measured atomic-force-microscopy profiles, we revealed that the roughened surface of steel develops periodic intensity distributions for subsequent pulses, leading to selective ablation for LIPSS formation. Contrary, aluminium’s rougher surface morphology induces incoherent scattering, leading to chaotic intensity distribution, explaining the lack of LIPSS regardless of thermal response.

By addressing the significant influence of material-specific single-pulse morphology, we propose a new pathway for optimizing LIPSS formation.

Time-resolved digital holography is a powerful technique for investigating surface dynamics during laser deep engraving, particularly the emergence of surface roughness components in the frequency domain. These components, whose underlying mechanisms remain poorly understood, significantly influence engraving outcomes. By employing time-resolved digital holography, we gain insights into the ablation dynamics, including the behavior of ejected particles and the resulting shockwaves. Furthermore, this method reveals the interplay between these dynamics and subsequent laser pulses interacting with the sample surface. Our study aims to elucidate the processes contributing to surface roughness development, offering a deeper understanding of the physical phenomena involved. These findings have the potential to improve precision and control in laser deep engraving applications, advancing both industrial and scientific practices.

Long standing open questions in ultrashort pulse laser processing include: What are the physical limits of ablation efficiency in air and liquid? What are the mechanisms of LIPSS formation and the incubation effect? With pump-probe experiments and time-resolved simulations we validate that a mix of spallation and phase explosion leads to the highest achievable ablation efficiency in air, which lies close to the energetics of evaporation, Further we prove with pump-probe microscopy that the redeposition of the spallation layer in liquid is supressing efficiency to about 20% of the air value. Finally by a combination of AFM and FDTD simulations we demonstrated that constructive coherent scattering from the ablation crater nanomorphology creates local field enhancements and surface plasmons which in return generate low frequency LIPPS by selective local ablation. In parallel local field enhancement is also one important contribution to incubation.

X-ray microscopy (XRM) is revolutionizing materials development, exploration, and failure analysis due to its non-destructive imaging and high resolution down to 50 nm. However, preparing cylindrical XRM samples with several tens of microns diameters poses significant challenges. Traditional methods like Focused Ion Beam (FIB) have mainly been used, which are precise but extremely time-consuming and unsuitable for high throughput. Addressing this issue, this study explores the application of femtosecond laser ablation in XRM sample preparation, emphasizing its advantages in achieving smooth, defect-free surfaces and precise material removal. Experimental results demonstrate the ability of femtosecond lasers to produce well-defined sample geometries, even in challenging materials such as metals, semiconductors, dielectrics and polymers, facilitating more accurate XRM measurements. Our findings underline the potential of femtosecond laser technology as a reliable, efficient, and versatile tool for enhancing XRM sample preparation workflows, paving the way for improved material characterization and advanced structural analysis.

The capability of OCT technology for real-time seam tracking and weld bead quality evaluation was examined in robot-guided automated GMAW and tactile laser welding and brazing of automotive parts made of bare steel, coated steel and aluminum with different joint types at different welding speeds. The permissible gap size and gap compensation were investigated for both automated conventional and tactile laser welding. During tactile laser welding and brazing, the filler wire speed and laser power were varied. Satisfactory results were achieved: The industry-proven, standardized OCT functions and fieldbus communication enabled accurate and consistent seam tracking, gap bridging and online quality monitoring of the seam topography of the tested materials during processing with variable welding or brazing parameters. Thanks to the flexibility, insensitivity to environmental conditions and very high accuracy of the OCT system, the joining processes could be precisely controlled.

This study aims to facilitate adaptive beam shaping using a deformable mirror for real-time control in laser butt joint welding by estimating gap widths. Two methods capable of real-time gap estimation were investigated: adaptive Kalman filtering and deep learning. The Kalman filter was evaluated experimentally, enabling adaptive beam shaping for gap bridging. Results demonstrated significant reductions in residual distortion and compliance with ISO 13919-1 Level D standards for joint gap widths up to 0.55 mm. Separately, deep learning methods, particularly Convolutional Neural Networks, were evaluated for gap width classification and tack weld detection, achieving over 99% accuracy under controlled conditions and 96% in noisy conditions. These findings highlight the potential of both adaptive Kalman filtering and deep learning for advanced gap characterization for real-time control, underscoring their roles in improving welding adaptability and weld quality.

During laser deep penetration welding, involuntary disturbances of the nominal process can lead to seam imperfections. Due to their possible impairing characteristics on the mechanical properties of the seam, it is of high interest to reliably detect these defects. This can be done by means of sensor based inline process monitoring. While the sensor data can be used to identify the defect location and perform post process repair work, it can also build the foundation to reweld the detected seam segments inline. This study demonstrates an approach to detect process anomalies during laser deep penetration welding of hidden T-joints inline and use a LabVIEW based control algorithm to utilize the scanning capabilities of the welding optic to reweld the defected seam area inline to enhance the seam quality and possibly eliminate necessary post process work.

The requirement of industrial development is comprehensively controlled production to ensure component quality despite short development times or due to batch fluctuations during production. Process evaluation through multi-modal sensor technology, real-time data processing and the use of artificial intelligence (AI) plays a decisive role in processing and control in order to ensure optimal process parameters. The paper presents possibilities for recording process emissions using sensor technology (e.g. acoustics, image-evaluation) for highly dynamic laser welding using 2D-scanner exemplary for copper. Furthermore, a real-time capable platform is presented, which is used for data acquisition and provides an interface for AI-based data processing for subsequent process control. The experimentally determined sensor data is used to establish a correlation between process quality of cop-per weldings and process parameters. The first AI-models developed in this way have been trained with an initial data set of approximately 160 trials and are currently in an evaluation phase.

To protect operators from laser radiation, laser machines must have a protective enclosure. The requirements for laser protective shielding are defined in the current standard EN 60825-4. According to this, extensive case-related laser stability tests must be carried out on the protective material. These case-related tests make it difficult to compare and select suitable materials and thus considerably increase the effort for manufacturers. Therefore, the SALSA project is taking a different approach: The influence of the beam diameter and the irradiance on the laser resistance of common protection materials is systematically investigated and the relationships found are expressed in simple mathematical formulas. This should enable manufacturers to use exemplary laser stability measurements to extrapolate service lifetimes for any operating conditions. The study describes the relationships found using green laser radiation, since laser radiation in the visible wavelength range is currently of particular importance for applications in e-mobility.

The increasing adoption of robotic laser welding highlights the need for robust seam-tracking systems to ensure precision and adaptability. Current methods struggle with fixturing errors, part-to-part variations, thermal deformation and the need for precise alignment of the laser beam, especially in three-dimensional welding scenarios. Laser welding is particularly sensitive to variations in joint morphology and material reflectivity, requiring advanced solutions to maintain high welding quality. Spatial beam shaping techniques, based on beam oscillation or “wobbling”, partially mitigate these issues by accommodating variable joint gaps and high-reflectivity materials. However, solutions, capable of real-time trajectory planning and adaptive process control, are essential to meet the requirements of this technology. This work presents a comprehensive analysis of the technological and computational requirements for seam-tracking operations, providing a foundation for developing systems capable of operating at high welding velocities, while ensuring quality and minimizing rework, paving the way for a more-effective implementation in smart-manufacturing.

This paper explores the feasibility of using High-Speed Laser Cladding technology to apply an enhanced nickel superalloy, Inconel 625, as coating material. This superalloy, which includes Reactive Additive Manufacturing additions, is designed to maintain high strength and corrosion resistance at both room and high temperatures. In this study, the effects of process parameters, such as laser power, powder flow rate and speed, were analysed for producing enhanced Inconel 625 coatings on 42CrMo4 steel cylinders. Single-layer coatings, extending 20 mm along the cylinder’s axis, were produced by High-Speed Laser Cladding process and systematically evaluated through metallographic analysis and defect identification. The coating process was optimized in terms of layer thickness, defect avoidance and powder catchment efficiency. The thickness of the selected coating layers ranged from 190 µm to 205 µm, with an average porosity between 0.16 % and 0.23 %. The powder catchment efficiency ranged from 71 % to 73 %.

Modern arc welding systems equipped with dynamic wire feeders enable the effective cladding of enhancing coatings while minimizing heat input to the substrate material, thus limiting its distortions. The heat input is related to the wire feeding rate through the synergic arc-voltage curves, and it defines the volume of the coating. However, low heat input is associated with rapid cooling, limiting the coating's homogeneity and producing highly quenched microstructures in the heat-affected zone of some steel substrates. An oscillating laser beam was employed as a secondary heat source to improve these aspects unless changing the volume of the coating. Laser-assisted and hybrid approaches in various setups were investigated during the cladding of wear-resistant Co-based alloy onto the martensitic steel substrate. The cladding process was monitored with a high-speed and thermal imaging camera, and the structure and microhardness of beads were evaluated.

Using high-speed laser melt injection (HSLMI), it is possible to generate wear-resistant metal matrix composite (MMC) surfaces on tools with excellent productivity. Since high laser intensities are required for the process, strong interactions can occur between hard particles and the laser beam. For reducing the interaction time and gaining a better understanding of the role of particle transport and incorporation in the HSLMI process, the trajectories of spherical fused tungsten carbide (SFTC) particles were analyzed using high-speed imaging. The trajectories were divided into a transport path and an incorporation path. The identified interaction mechanisms were particle deformation, formation of agglomerates and particle disintegration. The volume flow rate of the feeding gas was found to have a decisive influence on both the transport time and the incorporation time of the particles. Consequently, an increased volume flow rate led to a significant reduction in interactions between SFTC particles and the laser beam.

Cavitation erosion (CE) is detrimental to several engineering components, including ship propellers and pump impellers. Due to deformation and mass loss, CE significantly reduces serviceability, resulting in huge economic losses. This makes it essential to reduce the material damage caused by CE. Material damage can be minimised by using protective coatings to resist CE. Laser melt injection was performed to improve the cavitation erosion resistance. A metal matrix composite is formed by injecting spherical fused tungsten carbide and niobium carbide. The effect of different particle sizes on the CE behaviour of the reinforced surface layers were investigated. The microstructure of the modified surfaces was characterised using optical microscopy and image analysis. CE tests of the produced layers and untreated aluminium bronze were carried out according to ASTM G32-16 and the results were compared. The Niobium carbide coating was found to be the most effective in protecting substrates from cavitation damage.

Continuous market fluctuations, changes on product demand and global policies have led the automotive industry to look for innovative manufacturing solutions to improve manufacturing efficiency. In this sense, laser-based processes lead to shorter cycle times, less maintenance and more cost-effective production. Besides the laser technology is stated as key enabler of flexible, sustainable and reconfigurable manufacturing. In a group related to the authors different laser-based processes are being investigated aiming to modify the mechanical performance of automotive parts according to predefined requirements without any tool change. In this perspective, a multiprocess laser head able to perform laser heat treatment, laser remelting and laser wire cladding has been set up. First tests have been performed in CP800 high strength steel, looking for modifications in the mechanical performance of the material. This work shows the results of the metallographic and mechanical analysis performed on the first trials involving the multi-process tool with fast reconfiguration capabilities.

Laser welding, acknowledged for the low heat input process, was initiated to refurbish a steam turbine rotor. The refurbishment involved applying a superalloy filler metal to the damaged areas on the turbine disk caused by heavy rubbing. The post-weld heat treatment was established to minimize the residual stress after welding. The machining work was performed to remove cracks and finish the welded areas to original dimensions. The liquid penetrant test was conducted and revealed no defects. A notable characteristic of high hardness on the machined weldment was observed and attributed to a significant degree of work hardening. The maximum runout of the rotor was lower than that from the as received condition. The rotor mass unbalance was minimized and accepted according to the standard limit. The rotor then resumed operation for power generation. In addition, the consecutive projects showcased the success of laser welding in repairing critical power plant components.

Laser ablation of solids in liquids is a methodically straightforward and material-wise versatile method for synthesizing colloidal nanoparticles. Until now, this method has been difficult to access for researchers due to demanding laser operation conditions. In the last decade, compact, air-cooled and short-pulsed lasers with average power in the watt range became available. They are suitable for ablation and designed for integration. Fully functional systems for laser-based nanoparticle synthesis in 19" rack-mountable format are accessible. The integration of class 4 lasers in class 1 laser machines requires high safety measures, which were primarily implemented at the design level to be highly robust. Systems of light-sensitive detectors and controllable actuators make the sample production very reliable. An integrated autosampler enables the production of over 100 different samples in a single run. The device is a powerful tool for nanomaterial research for scientist from all application disciplines.

The search for materials with improved mechanical properties and functionalities has boost the development of advanced continuous nanofibers. The development of nanofibers and nanotubes predicted the production of new nano-composites with exceptional mechanical properties. However, the breakthrough predictions haven’t been achieved yet, in part due to the reduced length of the nanofibers or nanotubes, which restrained the mechanical reinforcement and manufacturing. Consequently, there is an enormous interest in the development of advanced continuous nanofibers, but conventional methods for fiber spinning cannot produce fibers thinner than some micrometers robustly. Here, we present two laser-assisted methods to produce nanofibers: Laser Spinning and COFIBLAS.

Both techniques will be explained as well as the potential applications of the nanofibers so produced in the biomedical field, textile field, composite manufacturing, etc.

Laser Surface Texturing (LST) has emerged as an innovative technique, enabling precise surface modifications at micro- and nanoscales to prevent bacterial colonization. This study examines the antibiofouling properties of laser-induced periodic surface structures (LIPSS) with a periodicity of approximately 700 nm, generated through femtosecond laser irradiation at 1030 nm. LIPSS were textured on a borosilicate substrate, used as floor of a 3D-printed four-channels microfluidic system exposed to Escherichia coli (E. coli). Two arrangements were investigated: longitudinal and transversal, i.e., parallel and perpendicular to the channel axis. Live-microscopy results show that LIPSS, being smaller than bacterial dimensions, effectively inhibited bacterial aggregation. Moreover, the transversal orientation of the LIPSS further improve their antibiofouling properties. This dual dependency on direction of flow highlights the critical role of morphology design in mitigating bacterial adhesion and biofilm development.

A donut-shaped laser beam has been shown to effectively alter the size distribution of nanoparticles synthesized by pulsed laser ablation in liquids. A significant decrease in particle size, a narrower size distribution, and an enhancement in sphericity when using the donut-shaped beam compared to the Gaussian beam is illustrated while conducting experiments on gold, yttrium oxide, and high-entropy alloy targets in water. We observe that the donut-shaped beam creates a toroidal-structured bubble that envelopes the ring-shaped ablation site, in contrast to the quasi-hemispherical bubble that covers the ablation spot produced by the Gaussian beam. This pioneering study can be a starting point for more investigations using higher temporal and spatial resolution.

A process of laser gas atomization (LGA) is presented for obtaining a spherical powder in a wide size range of 5 nm - 100 μm, in which laser beams conical geometry melt or evaporates or forms near surface plasma from wire in an inert gas flow conical geometry. The efficiency of the method is up to 0.5 kg/kWh . The method can be used to obtain powders from various materials - metals, ceramics, plastics.

The new method - laser centrifugal atomization (LCA) have been developed in which the end of a rotating hollow cylinder is melted, evaporates by a system of several lasers.

The productivity of obtaining powders from the melt (size 30-200 microns) will be up to 500 kg / h with an efficiency of 0.41 kW h / kg, and nanoparticles from the vapor plume or plasma - up to 150 kg/h with an efficiency of 0.87 kWh/kg.

This study presents the synthesis of dual-stoichiometry copper sulphide nanoparticles (CSNPs), featuring covellite (CuS) and digenite (Cu1.8S) phases, via laser ablation in DMSO using a 527 nm nanosecond pulsed laser. The nanoparticles (<30 nm) exhibit high absorbance in the second near-infrared window and photoluminescence, making them suitable for biomedical applications.

CSNPs demonstrated exceptional photothermal therapy potential, achieving a 52.2°C temperature rise at 1 mg/mL under 1080 nm laser irradiation, with high photothermal stability. In vitro, they induced significant cancer cell death under laser exposure while showing minimal cytotoxicity in the absence of irradiation.

Additionally, CSNPs enhanced contrast in photoacoustic imaging, outperforming ultrasound imaging. Their dual-stoichiometry extended absorption in the NIR range, improving photothermal and photoacoustic efficiencies. These findings highlight the promise of CSNPs as versatile agents for minimally invasive cancer therapies and advanced imaging, with potential for future in vivo applications.

Directed Energy Deposition with lasers using wire shows the potential of a good balance between accuracy and high deposition rates. To avoid defects and produce waste parts, inline monitoring is necessary to detect and counteract as part of inline quality control. In laser-wire processing, a risk of instability and fluctuations in wire incorporation can occur. In this work, the relation between melt pool dimensions and geometrical wire fluctuations was analysed using coaxial camera recordings. A melt pool width decrease of around 20% over less than one second indicated a subsequent movement of the wire from the center of the melt pool to the side, which is likely being caused by solid wire parts moving against solid material below the melt pool. As a consequence, a sudden wire movement lead to an increased laser energy input to the melt pool that increased the melt pool size and stabilized the process again.

Laser Powder Bed Fusion (PBF-LB/M) is a key additive manufacturing process for producing high-precision metal parts. However, its adoption is often constrained by production costs and the need to maximize return on investment (ROI). Increasing print speed is the most effective way to enhance profitability.

Beam shaping offers a straightforward solution by significantly boosting printing speed. When combined with a rapid switch to a small Gaussian beam for fine edge details, this approach increases production capacity by more than 50% for some specific parts, enabling ROI within months.

In this paper we will discuss the impact of differnt beam shapes across different PBF-LB/M applications, quantifying printing speed performance gains obtained on some specific parts and powders. We will at last extend this analysis to other laser-based manufacturing processes sush as DED-LB/M.

Fused filament fabrication (FFF) is a well-established additive manufacturing technique. Despite all the advantages of this process, the mechanical properties achieved are currently limited by a poor interlayer adhesion leading to low tensile strength perpendicular to the deposition direction (Z-direction). In this work, a versatile laser-assisted printing FFF system is designed for high performance and engineering thermoplastic materials printing optimization, such as PC with carbon-fiber reinforcement. The laser is used to pre-heat the material as it is being deposited by the extruder by locally melting the printed material to improve inter-layer adhesion and improve product isotropy. The temperature is monitored in situ using a thermal camera to optimize the laser preheating. The results show the improvement in the interlayer adhesion of the manufactured parts by laser-assisted FFF process, which is quantified by 50% tensile strength improvement, proving its potential for enhancing product performance for high temperature thermoplastics

Glass is frequently used in construction industry, both in facades and in interior fittings. The pane formats are limited as large glass panes would bend strongly. At TU Ilmenau a process was developed that enables the 3D-printing of glass stiffening ribs on flat glass using additive manufacturing. In a process similar to Laser Metal Deposition glass rods of 2 mm diameter are melted on their tip using a focused CO2 laser. The viscous glass is deposited on the moving glass sheets while further glass material is fed into the laser focus allowing a continuous printing process. The printing is carried out in a heated compartment which allows for printing of glass of high thermal expansion. So far, the process has been successfully implemented on model structures made of quartz glass, borosilicate glass and soda-lime-silicate glass. The printed structures are characterized by using photoelastic methods and bending tests.

Laser Glass Deposition is a promising technique for the chip-scale production of glass-based optical waveguide networks in which a fused silica (FS) optical fiber is welded onto a FS substrate using CO2 laser radiation. In this contribution, we investigate the impact of the CO2 laser radiation on the optical fiber’s waveguiding properties, particularly the propagation losses and mode characteristics. In a parameter study, we varied the CO2 laser beam parameters such as spot size, intensity profiles, wavefront curvature and optical power. Straight on-chip waveguides with a length of 100mm were fabricated and laser-cleaved for butt-coupling. Optimizing the process and beam parameters results in a fundamental mode transmission loss of less than 1.5dB at a wavelength of 1550nm, which includes coupling losses of about 1dB. These values are close to those of identical, unprocessed fibers, which exhibit losses in the range of 1dB at 1550nm in the same optical transmission experiment.

Al-Li alloys have received increasing attention for light-weight applications due to their low density accompanied by a high stiffness. However, the conventional processing of Al-Li alloys is still limited to Lithium concentrations below 9 at.%. The fabrication beyond this limit is desirable, because higher Lithium concentrations result in an increased mechanical performance.

Here we present laser-assisted additive manufacturing of binary Al-Li alloy powder with an increased Lithium content of 14 at.%. For the powder bed fusion process two different laser sources are compared: A cw laser at 1070 nm wavelength and an ultrashort pulse laser with a pulse duration of 250 fs at 1030 nm wavelength. The Lithium concentration of the additively manufactured parts is determined by laser-induced breakdown spectroscopy. The influence of the laser source on the microstructure and mechanical properties is investigated.

Lasers emitting short pulses, with wavelengths ranging from UV to NIR have been demonstrated to be effective to remove debris or contamination deposited on the architectonic elements, such as graffiti, patinas, black crusts and chewing gum. Here, we present an alternative laser cleaning method to remove chewing gum encrustations on natural stone, based on the use of a continuous wave, low power CO2 laser. The encrustations of chewing gum are mainly composed of their rubber or elastomer components which strongly absorb the CO2 laser radiation. Additionally, we propose a method for rapid assessment of the cleaning level based on hyperspectral reflectance imaging. The results obtained have been confirmed using characterization techniques commonly used in the cleaning level determination: stereomicroscopy, profilometry, Raman spectrometry and Fourier-transform infrared spectroscopy. This non-invasive method of cleaning control will allow real-time control of the cleaning process, avoiding over-cleaning or insufficient cleaning.

Goal of the investigations was to develop a laser-based, additive-free joining process for cellulose-based materials such as paper and cardboard. Previous investigations have shown that paper quickly transforms into liquid and gaseous reaction products when irradiated with CO laser radiation, which can be used for joining in a heat-sealing process.

In the current project, the process is being further developed with a view to increasing the joint strength and using standard industrial papers. Laser parameters and paper materials were varied and the influence on the joining result and the chemical material conversion was analysed. It was possible to realise joints whose strength was hig-her than that of the paper material itself.

The process will be implemented in a demonstrator plant with the aim of producing product packaging. A major advantage of the process is the water-solubility of the paper's own adhesive, which does not impair the recyclability of the paper.

Thermoplastic coatings are highly valued in various industries for their ability to protect surfaces against corrosion and minimize excessive wear. Laser-based directed energy deposition of polymers (DED-LB/P) represents a promising method in this respect, offering the ability to realize partial coatings, selectively adjustable layer thicknesses and structure widths, and beyond that, complex three-dimensional structures. In the present study, a common directed energy deposition machine equipped with a high-power diode laser (Pmax = 4 kW), a rotating plate powder feeder and a discrete coaxial powder nozzle was used to produce carbon black/polyamide 11 coatings on metallic substrates. The high laser power available for polymer processing allows a large laser beam diameter (d = 10 mm) to be set, resulting in a high deposition rate and improved powder catchment efficiency. The coatings produced are evaluated for surface quality, density, and bonding defects to verify their performance and reliability.

In this work, we explore the use of a femtosecond laser operating in the GHz burst regime for metal polishing, both with and without ablation, to enhance micromachining quality. The high number of pulses per burst (800 ppb) combined with high burst repetition rate (800 kHz) allows for ideally distributing the laser energy over metallic samples. As surface melting and smoothing is driven by surface tension forces, this is a critical factor in this process. Recent studies have demonstrated that GHz bursts of femtosecond pulses are particularly effective for metal polishing, as the pulse-to-pulse delay within the burst is shorter than the material's characteristic heat relaxation time. We will present our results on stainless steel and titanium and point out the best process windows.

Laser polishing of metals is a multi-step process requiring detailed and individual parameter optimization for each processing step. The experimental approach to parameter optimization for new materials and initial surface roughnesses is not optimized itself. Therefore, high numbers of experiments are necessary. Furthermore, established approaches neglect that laser polishing is a multi-step process, resulting in redundant experiments and suboptimal roughness. In this work, a new approach for optimizing and benchmarking the parameter optimization process is developed. This approach is based on experiment simulation using a dataset of 2,600 conducted experiments on laser polishing of 1.2343. Thereby, it allows for cost-free optimization and comparison of parameter optimization strategies. In the benchmark a wide range of conditions such as experiment limitation and target roughness were tested. As a result, the domain-based approach could find parameters meeting the criteria in less than 100 experiments even for a suboptimal choice of initial algorithm values.

Laser-based optical manufacturing enables efficient production of high-precision optical components through processes like selective laser etching (SLE), laser ablation, and laser polishing (LP). At the Institute of Microtechnology and Photonics (IMP), we focus on combining SLE with laser polishing for miniaturized optics. Studies show that the one-shot LP strategy outperforms scanning LP by preventing mid-spatial frequencies. However, achieving uniform polishing remains challenging due to the Gaussian beam profile, which causes uneven polishing across the lens surface. While diffractive optics can improve power distribution, they are costly and often differ in practice. We present a novel approach called Quasi-Beamforming, utilizing galvanometric scanners to create a tailored thermal distribution for uniform polishing. This strategy is demonstrated on a convex, rotationally symmetric surface, applying a “sombrero” thermal profile to achieve smooth, high-quality optics.

Internet of Things (IoT) applications demand antennas that can integrate into diverse environments. Traditional rigid antennas struggle to conform to curved surfaces, bendable devices, and wearable applications. Flexible antennas offer a compelling solution by overcoming these constraints, enabling seamless integration into various unconventional form factors.

In this work, we report the results of experiments on the application of selective surface activation induced by laser (SSAIL) technology for antenna applications. The inverted F antenna on the Polyvinylidene fluoride (PDVF) substrate was modeled using CST Studio software. The surface of (PVDF) was processed using 532 nm femtosecond laser Femtolux (Ekspla) irradiation. Later, irradiated areas were selectively coated by copper layer using surface activation and electroless plating process.

The S11 parameter of the manufactured antenna was compared to the modelling results. Measurement results were in great agreement with the simulation results. Antenna bandwidth at -10 dB was from 3.35 GHz to 3.72 GHz.

III-V semiconductors (e.g. GaN) are playing an increasingly important role in LED technology and in high-power electronics. However, the current production of these semiconductor devices requires many individual process steps, including lithographic prestructuring of growth substates, which is very cost- and energy-intensive. The targeted laser structuring of substrates in both the micro and nanometer range should enable the production of high-quality layers in isolated dies in a closed process and thus significantly reduce both costs and environmental impact.

With the help of a UV ultrashort pulsed laser, wide tracks are written on various substrates (e.g. sapphire or silicon wafers), which selectively prevent subsequent epitaxial overgrowth and thus enable bottom-up separation into individual dies. Subsequently, nanostructuring is carried out within these dies to enable the overgrowth of high-quality layers. Furthermore, the scalability of this structuring, e.g. with the help of phase masks, and the influence of different processing atmospheres is investigated.

Photoelectrochemical (PEC) etching offers a damage-free surface and high horizontal selectivity which dissolves the light-illuminated areas. However, accurate etch-depth control is challenging due to the absence of a mechanism to limit etch depth. The evanescent light localizes the illuminating area to the vicinity of the interface under the total internal reflection. Owing to the dependence of the etch rate on the light intensity, the etch depth is expected to be restricted by the localization of evanescent light. In this presentation, we demonstrate PEC etching using evanescent light. The cavity shape reflects the distribution of evanescent light, implying a sufficient etchant supply. The time evolution of the etch depth revealed that the evanescent light distribution limited the etch depth to approximately 900 nm from the reflective interface. This evolution matches the model, stating the etch rate is proportional to light intensity. Our results lead to precise etch-depth control and damage-free planarization.

Integrated sensors are becoming increasingly important for structural health monitoring of components. Digitally printed and additively manufactured strain gauges can be used to evaluate the mechanical stress of materials with a greater quality factor than manually applied strain gauges.

We propose an approach that involves the application of strain gauges to tensile stress components using the ink jet-printing process with a nanoparticle silver ink. In a post-processing step, the strain gauges are laser-sintered to functionalize the material and stabilize the resistivity of the thin film. We report on the results of tensile tests with the contacted sensors and characterizing their electrical properties, as well as the proportionality factor of the strain gauges in dependence of the laser process parameters.

Our approach with contactless application and laser-based post-processing has the potential to enhance the reproducibility of the sensor application and strengthen the quality assurance.

The application fields of silicon carbide (SiC) range from high-performance electronics, power semiconductors, and batteries to use in quantum computing. Due to its outstanding properties such as very high hardness and abrasion resistance, silicon carbide is a hard-to-machine material. One possible processing method is high-precision laser ablation with ultrashort pulses.Investigations were performed on the materials 4HN-SiC and 6H-SiC to study material modifications by picosecond laser excitation at 355 nm and 266 nm. Confocal microscopy, scanning electron microscopy, and mass spectrometry were used to determine the ablation threshold fluence and ablation efficiency, study the morphology, and analyze the Si/C ratio changes in the laser-affected area. In summary, silicon carbide's unique properties present challenges in material processing. However, the use of picosecond lasers with Deep-UV wavelength can lead to improved processing results, enhancing its application possibilities in various high-tech fields.

The manufacturing process of 4H-SiC wafers involves slicing the wafers from an ingot using laser cutting, followed by polishing to achieve the required flatness. This study explores the feasibility of micro-polishing 4H-SiC surfaces using femtosecond laser vector beams in combination with wobble-based scanning. Initially, structures measuring tens of micrometers were fabricated using a high fluence of 1.39 J/cm², resulting in a surface roughness (Sz) of 32.3 μm, which replicates the surface morphology of 4H-SiC after laser slicing. Subsequently, a lower fluence of 1.25 J/cm² and defocus were employed to create a smoother surface morphology with a surface roughness (Sz) of 7.7 μm. This approach demonstrates that femtosecond laser vector beams combined with wobble-based scanning can effectively perform micro-ablation on SiC surfaces, highlighting its potential for 4H-SiC micro-polishing applications.

Recent work has shown the possibility of hybridizing directed energy deposition (DED) processes, with interlayer plastic deformation to refine the grain structure and improve mechanical properties. The plastic strain stored in the build during deformation can trigger recrystallization under the inherent heating from subsequent laser deposition, leading to a finer, more equiaxed grain structure. In this work we study the effect of the deformation level on the final microstructure evolved by applying interlayer hammer peening to laser DED fabricated Inconel 625. Microstructural evaluation indicates that under extreme deformation levels, a fine grain structure of ~3μm is formed. Further analysis also reveals that the complex thermal conditions imposed by the laser, lead to a heterogeneous grain distribution consisting of both recrystallized and non-recrystallized grains. The results of this work highlight the possibility of spatial microstructure control through interlayer deformation and elucidate some of the process-microstructure relationships.

In recent years the demand in Smart and Technical Textiles increased, especially with incorporated sensors and actuators. However, current conductive textile structures, achieved by integrating conductive yarns, wires and strands or by conventional coating and printing technologies, lack kink resistance and reliability. The latter do also lack the needed grade of functionalization.

The proposed process allows the application of a multi-material powder compromising a blend of a polymer powders and a high amount ( > 50 wt%) of functional pigments e. g. metal particles.

The technology is based on a nozzle based application of the lose powder mixture and a subsequent laser fixation step. This enables the fabrication of individualized and highly functionalized coated substrates based on a digital data set.

The Directed Energy Deposition (DED) process is highly influenced by the mass flow of metal particles. Higher mass flow increases productivity by creating thicker layers but also complicates melt pool stability due to residual heat accumulation in the solidified material. This overheating disrupts thermal properties, affecting the fluidity of the liquid metal and potentially destabilizing the process, leading to defects or geometric inconsistencies.

This study presents an advanced thermal model incorporating domains with adjustable properties to simulate the part's growth and address these challenges. A virtual closed-loop PID controller is integrated into the model to calculate optimal laser power in real time, compensating for accumulated heat and maintaining a stable temperature in the laser-material interaction zone.

Experimental validation confirms that applying the model's predictions ensures process stability, enabling the production of components with consistent quality and desired properties.

Blister-Actuated Laser-Induced Forward Transfer (BA-LIFT) uses a polyimide layer to decouple laser-material interaction, enhancing control over transfer dynamics. This study combines experiments and simulations to analyze blister formation and its role in material ejection. High-speed imaging reveals oscillatory blister behavior, modeled using polynomial fits for numerical predictions. A Phase-Field model in COMSOL Multiphysics simulates jet formation and secondary effects, incorporating cavitation bubbles observed experimentally. Findings suggest that the blister-induced velocity field triggers cavitation at the polyimide-fluid interface, impacting transfer efficiency. Additionally, investigations into LIFT for high-viscosity pastes show that substrate spacing dictates whether material forms a continuous jet or disperses. A novel FEM-CFD model enables printability maps predicting paste behavior. These insights improve predictive control and optimization of LIFT techniques, broadening material applicability.

This year the author's company celebrates its 30th birthday and with it a lengthy period in which countless process faults have been found. The ongoing development in laser sources, processes and applications continuously offers new challenges for the photodiode-based process monitoring to find even the smallest deviations. Especially in applications with many weld seams, such as batteries or bipolar plates, not only detection but also classification is required to quickly identify the root causes of faults.

In this study, a conventional broadband approach is compared to a multi-spectral monitoring. Welding experiments are carried out with highly electrically conductive materials using two sensor systems. The experiments are then evaluated for both systems and the results are compared to identify the individual benefits of the sensor approach. As a result, the multi-spectral system is particularly beneficial when it comes to classifying and differentiating between faults which enables individual rework strategies for production.

We present a novel Optical Coherence Tomography (OCT) system for industrial metrology with higher imaging power (>50 mW) and greater imaging depth field of view (>30 mm) than any existing industrial OCT system. This system includes a low noise fiber amplifier to generate an imaging light source with very high power (>60 mW) suitable for OCT imaging with sensitivity > 100 dB. Using this system and a 50 kW Yb:fiber laser, we have produced in situ direct measurements of laser weld keyhole geometry exceeding 40 mm in depth. This represents the deepest in situ direct keyhole measurements performed to date without the use of X-rays. The capabilities of this system extend the application space for in situ weld monitoring of laser processes with OCT.

In laser deep penetration welding a constant weld depth is an essential quality measure that is usually obtained by on-line process monitoring techniques such as optical coherence tomography (OCT). However, due to the lack of referential information about the keyhole shape, the extraction of meaningful information about the keyhole from the OCT signal is limited to the keyhole depth which is acquired by means of statistical analyses. In this research on-line X-ray-recordings alongside OCT measurements were conducted during the welding of pure aluminium (EN AW-1050A) in the Rosenthal regime to enable a more profound interpretation of the OCT signal. The comparison between both measurements enabled a correlation between geometric keyhole features and characteristics of the OCT frequency analysis, resulting in an improved time-resolution for the extraction of the keyhole depths. Furthermore, metallographic longitudinal cross-sections were used to investigate how close the keyhole depth is linked to the actual welding depth.

Laser beam welding offers unique capabilities for producing components in several industries, such as electric vehicle battery manufacturing. However, the high solidification rates and high coefficient of thermal expansion when welding 6082-T6 aluminium alloy result in strains that lead to hot cracking. This highlights the need for cost-effective process monitoring approaches. Optical systems such as high-speed cameras and sensors, including infrared and acoustic emission, are capable of monitoring strain-induced hot cracking. However, most of these methods are limited to surface region and are unable to investigate the sub-surface solidification dynamics where hot cracks originate. Therefore, high-speed X-ray diffraction is used for measuring sub-surface strain and stresses, but the process is time-consuming and expensive. Physics-informed models have emerged for reconstructing sub-surface dynamics using surface data from sensor measurements, however, these methods are still inaccurate. Hence, the present review explores machine-learning approaches for correlating real-time surface measurements with complex XRD-derived sub-surface dynamics.

Welding of aluminium alloys from the 6xxx series is challenging due to the formation of hot-cracks, however, their favorable mechanical properties require laser micro welding processes for housings in battery technology or microelectronics. In that regard, The determining factors for hot crack formation are residual strains and stresses that occur during solidification. In order to examine these in more detail, in-situ and ex-situ investigations using the high-energy X-ray diffraction beamline ID31 at the European Synchrotron Radiation Facility were conducted. The measurement data provided the possibility to calculate temporally and spatially resolved stresses in welding direction and in z-direction. Various prevention strategies, such as laser pulse modulation and application of an additional heating laser in various alignments were used to determine their effect on the residual stresses and hot crack formation. In addition, microsections allowed further insights on phenomena related to the melt zone and the heat affected zone.

Pyrometric temperature measurements are essential for quality monitoring of laser processes, but still face some major challenges. Temperatures usually need to be measured with high accuracy and high spatial resolution due to the typically small process scales of laser processes. However, the temperature accuracy is affected by the angle-dependent emissivity, which can lead to incorrect temperature measurements if the local inclination angle changes, and the spatial resolution is limited by the measurement spot size, leading to reduced spatial resolutions for larger spots.

This contribution addresses these issues and presents a method to correct the angle-dependent emissivity by simultaneously measuring surface temperature and geometry, and a method to increase the spatial resolution by compensating for the effect of the transfer function of the system, caused by the size of the measurement spot, using a reconstruction algorithm. The results show good agreement with reference measurements, demonstrating the effectiveness of the proposed methods.

Femtosecond lasers have a role to play in the improvement of electrodes manufacturing for current and future generation of batteries, to increase batteries safety, lifetime and reduce wetting and charging time. The design of suitable structuring patterns for the required high processing speeds is a current development topic, the laser ablation parameters are always key parameters. Our study is using fs lasers up to 300W mean power, that can be coupled to a SLM (Spatial Light Modulator) to divide the incident beam in up to 50 beams. The electrode production speed is decisive to be economically credible. Both electrode cutting and electrode structuring results will be presented and discussed. Because of the huge ablation efficiency difference between the active material and the metallic substrate, electrode cutting time is dominated by the metallic substrate cutting for which a significant benefit of GHz bursts is evidenced.

Increasing the available energy and power of femtosecond lasers has consistently enabled new applications in micro-processing. This article explores the use of beam shaping with high-energy industrial lasers, addressing the challenges that arise when scaling energy levels for robust industrial implementation.

For the first time, a passive beam stabilization system based on Multi-Plane Light Conversion technology has been demonstrated at 400 µJ in the infrared. Passive stabilization is crucial for ensuring a reliable process, as it maintains stable beam shaping under all conditions without requiring realignment after installation. This stabilization is combined with high-quality square top-hat beam shaping, achieving sharp transition zones of 15 µm for a 60 µm top-hat in the processing plane and a beam uniformity of 0.07.

The article will discuss process improvements enabled by beam shaping, with a particular focus on enhancements in LIPSS generation compared to conventional processing methods.

With the production speed being a major obstacle in the economic production of PEMFCs (Proton Exchange Membrane – Fuel Cell), introducing laser based drying of the coated catalyst layers could bring drying times from minutes down to just a few seconds. Laser based drying is also a more energy efficient alternative to oven drying and has a much smaller footprint.

In this paper we present the effects of the laser irradiation on the catalyst layer, demonstrating the degree of drying and the microstructure of the laser based dried catalyst layers at different drying temperatures and interaction times. For this purpose, a 980 nm diode laser with a temperature closed control loop is used to dry screen printed catalyst layers in a semi-continuous process.

The increasing need for energy storage devices demands efficient battery production technologies. One key process is drying anode and cathode slurries, usually done via convection-based ovens, which are space and energy consuming. A more efficient method is laser-based drying, which can process water-based slurries in a continuous roll-2-roll process.

A laser drying module developed by the authors offers rapid drying at web speeds up to 5 m/min and > 50 % reduced drying times. The study examines the interaction between laser radiation and slurry components, with a focus on preventing damage to the anodes. Processing parameters, including drying temperature, web speed, and film thickness, are adjusted to examine their impact on the anode. Since high evaporation rates may cause binder migration, the adhesion of the anode to the current collector foil is measured. The findings suggest that rapid drying with laser radiation can be successfully implemented under the right conditions.

High-power industrial femtosecond lasers require spatial beam shaping to efficiently distribute laser intensity for surface patterning. Although spatial light modulators (SLMs) offer this flexibility, their limitations (resolution, aberration) can affect the experimental intensity compared to the desired distribution (e.g., loss of multispot array homogeneity) and reduce overall efficiency due to energy loss in the stray 0th order. Automatic feedback strategies have been proposed, enabling dynamic correction of SLM modulation based on real-time laser intensity observation, potentially compensating for non-homogeneities.

By implementing this method numerically and experimentally, we evaluate its performance in overcoming SLM limitations. Laser intensity distribution analysis reveals the constraints on the achievable number of parallel spots, their homogeneity, and energy efficiency. Advanced surface patterning is achieved using this method. The results highlight both the potential and the limitations of automatic phase mask optimization in addressing SLM shortcomings for robust surface structuring with ultrafast lasers."

In the automotive industry, the increasing number of product variants requires a high degree of flexibility, offering new applications for additive manufacturing processes. A promising and cost-effective approach is the hybrid additive manufacturing of tool components using directed energy deposition (DED). A key factor in the process is the laser power, as the temperature gradient between substrate and additive build-up has a significant influence on the formation of cracks and the contour accuracy of the component. In this paper, a laser power control system is investigated with the aim of keeping the melt pool temperature constant to reduce geometric deviations and residual stresses resulting from excessive heat input into the component. For this purpose, welding specimens are manufactured additively, followed by an optical measurement and a metallographic analysis to identify part defects. The results are used to produce a tool component with an optimized hybrid additive manufacturing strategy.

Laser cladding technology using wire is a modern technique for surface enhancement and repair. This study investigates the cladding process using steel 42CrMo4+QT as the base material and stainless steel 316L as the additive material. A pyrometer and infrared camera were used for monitoring the process. The pyrometer provided real-time measurements of the melt pool temperature, while the thermal camera provided a detailed view of the heat distribution and cooling dynamics. A key focus of the research was to analyse how heat accumulation affects the measured quantities and influences the technology outcome. By investigating the interplay between thermal parameters, heat accumulation and cladding quality, the study identifies critical quantities for optimising process control. These findings will help to advance the application of LMD wire technology in industrial surface engineering.

Material extrusion is a widely used AM process and is gaining more acceptance in industry applications due to its material variety, flexibility, and low cost. However, its usage is limited by a process-related anisotropy caused by insufficient interlayer bonding due to reduced temperature in the process zone. To enhance layer adhesion, an adaptive laser preheating system is integrated in a conventional printhead around the extrusion nozzle. The setup with eight fiber coupled diode laser allows preheating in feed direction and investigation of various intensity profiles. The article describes the experimental setup and significant improvements achieved. Laser preheating with different intensity distributions (spot, sickle or ring shaped) show an incasement of up to 85 % of the mechanical properties in the build-up direction. However, due to the additional energy input by the laser, controlled cooling of the workpiece becomes a crucial factor and is investigated as well.

In laser powder bed fusion (PBF-LB/M), the adjustment of the microstructure by parameter variation is limited by process stability and it’s resulting part quality. By combining PBF-LB/M with ultrashort laser ablation, these limits can be exceeded by transiently involving additional heat dissipation structures or slits, which act as heat barriers. These additional structures can be removed during build-up.

The microstructure adjustment in AlSi10Mg components manufactured by combined additive and subtractive (AddSub) laser material processing was the focus of experimental and numerical investigations. Different heat dissipation structures with varying geometries and ablation strategies were manufactured and subsequently metallographically analyzed including hardness measurements. The employment of these structures leads to an altered local temperature field, consequently affecting the solidification conditions. A comparison was made between conventionally manufactured parts by means of PBF-LB/M and those produced using the aforementioned methods.

In PBF-LB/M, pulsed modulation leads to higher cooling rates and refined microstructures due to altered solidification conditions. Introducing laser-off times suppresses heat accumulation and improves manufacturing accuracy. However, it also decreases productivity due to laser-off times and lower scan speeds compared to conventional PBF-LB/M processing. Achieving comparable build-up rates requires a holistic approach to process and system technology development. Fraunhofer ILT has explored pulsed melting in PBF-LB/M using an ultrafast laser beam deflection, establishing a pulsed melting process with a continuously emitting cw laser source. Experiments indicate that traditional parameter settings must be reevaluated, particularly regarding spatial and temporal interactions of multiple melt pools, the powder layer, and shielding gas flow. This article presents initial investigations and discusses the process observations and analysis of first samples.

Here, we explore advanced technical solutions for integrating laser micro-machining processes into an SLM 250 machine, creating an efficient and precise hybrid system. The integration involves adding an IR fiber laser (nanosecond or picosecond) with 30-100W power, coexisting with the CW fusion laser. Both utilize the same beam shaping and movement equipment, including a galvanometric head and F-Theta lens. We've modified the control system to enable swift transitions between SLM and micro-machining modes between layers, enhancing process synchronization. To achieve extremely precise control over laser beam position, size, and shape, we've developed a tool capable of characterizing both continuous and ultrashort pulse laser beam profiles up to 100W. The integrated micro-machining process is being tested to improve layer surface roughness and precision, particularly for micro-channel resolution. This hybrid approach promises to significantly enhance the capabilities of additive manufacturing, offering new possibilities for creating complex, high-precision components with superior surface quality.

The drying of lithium-ion battery electrodes is one of the most energy- and cost-intensive processes within the battery production chain. Recently, laser drying has emerged as a promising energy-efficient alternative to the conventional convective and infrared drying methods due to its direct energy input, high energy density and superior controllability. However, the underlying process mechanism remain incompletely understood, and its full potential has yet to be reached. In this work, a numerical process model was developed to simulate the changes in evaporation rates, film thickness as well as the film tempera-tures, while also estimating the process duration and energy consumption for both laser and convective drying methods. Comparative analysis was made between two drying methods in terms of their process durations and energy consumptions. Furthermore, the process disturbance in the coating and drying processes was addressed, and a concept of model-based process control was developed.

The most reported approaches for controlling the laser welding process are the application of data-driven proportional-integral-derivative (PID) controllers. These methods allow controlling the desired weld quality using direct or indirect measurements of the melt pool as feedback signals. However, these approaches fail to generalise away from this training data. With the raise of scientific machine learning, physics-informed neural networks (PINNs) for control systems is gaining popularity. The fundamental idea is to embed the governing equations of the laser welding process into the machine learning model, i.e., a specified neural network. This paper aims to critically review current developments of PINNs for real-time control of the laser welding process. The discussion will highlight the accuracy of prediction, generalisation to un-seen events and computational latency. A series of use cases with a moving Gaussian beam and a set of shaped beams will be presented to support the findings.

The growth of e-mobility has driven a rising demand for copper welding, a process made difficult by copper’s high reflectivity and thermal conductivity, which often lead to defects like porosity and spattering. Beam shaping enhances weld quality by optimizing energy distribution. Multi-Plane Light Conversion technology offers exceptional flexibility in beam shaping, making it essential to determine the most effective beam configurations.

This study explores multi-physics simulations of various beam shapes, including asymmetric designs, and their impact on key weld seam characteristics such as capillary stability and surface finish. We will outline the process for identifying an optimal beam shape, examine how to adapt it into a manufacturable design, and discuss criteria for evaluating its performance against other configurations, including symmetric shapes and unshaped beams.

During laser welding, droplets can detach from the melt pool, which may impair the surface quality or the mechanical properties of the weld due to lack of material. Many techniques to reduce spatter are either increasing the melt pool size to reduce melt flow velocities, or increasing the capillary aperture size to reduce the vapor flow velocity. However, these strategies add complexity to the welding setup and reduce its flexibility. This work applies coherent beam combining technology in order to optimize the intensity distribution during laser welding of AISI 304 stainless steel at 12 m/min welding speeds with respect to the successfully deployed optimization presented in literature. The formation of spatter during the welding process was captured by means of high-speed video recordings. The results show a reduction of spatter by 85%, when welding with the optimized beam shape, compared to a static circular beam shape.

Beam shaping presents promising new horizons for laser materials processing. In particular, the potential to manipulate heat and mass flow during welding and additive manufacturing processes. In this work, we explore whether static beam shaping can be used to control solidification conditions by modulation of local heat and mass flows computed by fluid dynamics. By manipulating beam profile, we explore the interplay of simultaneous beam shaping and process parameter optimization to influence the thermal field and solidification parameters, G and R. The CIVAN laser system offers the ability to control both static and dynamic beam shape properties and thus offers an enormous parameter space to explore. We present a simple taxonomy of beam shape topologies and symmetries and then use it to constrain and systematize our shape space exploration. We control the shape space exploration using a Monte Carlo based trial shapes and test them in a fluid dynamics simulation.

A novel measurement method was developed to indirectly measure the absorptivity of liquid metals, including its dependency on the angle of incidence and the temperature. For the method a small metal piece is molten. Surface tension forms the liquid metal to a spheroid droplet. The thermal emission of the droplet is recorded at the desired wavelength after a linear polarizer with a camera without any probe beam. The refractive index n and extinction coefficient k can be determined by analyzing the intensity of the p-polarized thermal emission over the curvature of the sphere. The temperature was determined via quotient pyrometry, which was included in the same optical setup. In the talk we show the successful application of the method for the determination of the absorptivity characteristics for liquid copper at a wavelength of 850 nm.

A method for determining material hardness of metals is based on laser-induced shockwaves generated with a pulsed TEA-CO2 nanosecond laser. The laser creates a plasma, which interacts further with the laser beam and subsequently generates a shockwave. The shockwave is ignited above a spherical indenter, made of Al2O3, which is pushed thereby into the metal surface. The indentation geometry can be analyzed to draw conclusions about material properties. The process duration depends mainly on two factors: Generating and analyzing the indentations. To speed up the indentation process an approach with a constant movement of the specimen during indentation was tested. The results indicate that velocities up to 1.8 m/min do not have a significant influence on indentation diameter and depth. Therefore, positioning times with acceleration and deceleration can be avoided and thus up to 30 indentations per second with a distance of 1 mm between each indentation could be realized.

Precise 2.5D microstructure fabrication on large areas (>1 m²) remains a challenge for industrial applications. Using a 248 nm KrF excimer laser with grayscale masks, we successfully created sub-10 µm asymmetric microstructures on polycarbonate sheets. Grayscale mask features modulated the laser fluence, enabling depth variation for 2.5D shapes. For large area substrates, a floating objective head mitigates substrate thickness variations, ensuring focus over large areas. The incubation effect was exploited to enhance material absorbance, allowing controlled microstructure formation at sub-threshold fluences. Replication into PDMS confirmed the fidelity of fabricated structures. This work demonstrates a scalable and precise fabrication method for creating sub-10 µm asymmetric microstructures, addressing critical challenges in advancing industrial applications such as functional printing, optics, and microfluidics.

It is widely accepted that the femtosecond laser damage resistance of thin films is primarily influenced by factors such as material bandgap, electric field intensity, and the structure of the thin-film stack. With all these being optimized, it is found that the thickness of overcoat plays an interesting role in this as well. Unlike a thick overcoat, a thin overcoat can noticeably reduce both the laser damage resistance and fatigue performance, even when the overcoat layer is deposited with wide bandgap material and subjected to minimal electric field intensity. This phenomenon is being investigated as a factor of thin film optimizing for ultrafast laser applications.

Glass etching using a short wavelength laser in combination with an absorbing top-coat is re-visited. We wanted to refine the process and understand the mechanism that creates shallow structures without the need of subsequent gaseous or wet etching of the glass.

A porous particulate film of 99% carbon was deposited on a 0.15mm thick glass slide. A violet wavelength multi-mode laser with micro-spot optics focused a square 10um spot on the absorbing film stack. After exposure, the remainder of carbon is removed, and smoothly etched lines in the glass are observed. AFM and optical profilometer measurements showed V-shaped trenches 4 to 5um wide, 100nm deep, with the built-up material along the grooves around 25nm in height, and a RMS roughness in the channel of 6nm. Possible applications of this cost-effective technique for life-sciences structured substrates, for micro-fluidics, or as re-distribution layers in stacking of semiconductor chips are presented.

Diamond-like carbon (DLC) coatings and laser texturing are strategies used to improve the performance of functional surfaces in a wide range of applications, such as automotive, aerospace, cutting tools, optical devices and medical implants. They have mainly been exploited independently but, recently, a new approach combining DLC coating and laser technology to further enhance performance is being explored. In this work, three different strategies to obtain nanostructured DLC coatings on polycarbonate (PC) substrates are studied. Laser-induced periodic surface structures (LIPSS) generated on the PC substrate, both those created directly by a UV source and those replicated by hot embossing from a mould, and then transferred to the DLC coating, and LIPSS induced directly on the surface of the DLC coating are compared. SEM and optical profilometry are used to analyse the generated structures, while EDS analysis is used to evaluate the chemical changes produced in the DLC coatings.

The employment of ultrashort laser pulses has enabled the fabrication of grating structures on a shape memory material, suitable for strain measurement via the interference pattern. This development signifies a novel application of laser-generated microstructures and facilitates direct strain measurement on the object without the necessity of an additional layer, as often required by conventional methods. The grating constant was varied between 5 µm and 10 µm. Furthermore, Laser Induced Periodic Surface Structures (LIPSS) has been demonstrated to function as a structure for the purpose of producing lower grating constants. The employment of LIPSS has been demonstrated to result in a grating constant reduction to approximately 620 nm. Moreover, the employment of LIPSS eliminates the requirement for monochromatic light in strain measurement applications. Illumination with a white light source leads to a color shift in the reflected light, which depends on the degree of stretching.

The increasing demand for large, complex metals parts requires enhanced productivity and cost efficiency — goals that conventional Selective Laser Melting / Laser Powder Bed Fusion (SLM / LPBF) cannot fully achieve. The innovative Macro-SLM machine concept addresses this challenge by integrating high-power laser systems with cost-effective coarse-grain metal particles. This combination merges the complexity of SLM-parts with the efficiency of direct energy deposition. As a result, Macro-SLM significantly reduces production costs for large, complex metal parts. Components with a dimension in the cubic metre range can be built at rates up to 10 kg/h. This work presents the Macro-SLM setup and experimental results for steel samples. Tensile tests demonstrated that the mechanical properties of the as-built samples exceed the required standards. Additional data is provided for fatigue and hardness tests. The potential of the Macro-SLM process is further illustrated by full size prototypes of industrial parts.

The repair of turbine blades is essential for their sustainability, especially in the aerospace industry where their manufacture is both costly and effortful. Recent advancements in machine development led to the development of the MESSIAH system, which has the potential to repair large metallic components up to 2,5 meters high using powder bed fusion with laser beam for metals technology. However, the planning of repairs, the preparation of components and the compatibility of materials are still aspects of the MESSIAH system that haven't yet been considered adequately. This contribution provides a feasibility analysis and initial findings on using the MESSIAH system for the repair of turbine blades. The results provide insights into the potential and limitations of using the system in the repair process chain and give initial recommendations for its optimization. These findings provide a basis for improving repair strategies in order to increase the lifetime of the components.

Due to the limited production rates of AM technologies, like LPBF, the market and investment hype of AM has come to the slope of enlightenment, moving towards the plateau of productivity.

To further increase the diversity of AM machine designs and to solve limitations of conventional LPBF the authors have rethought the kinematics of LPBF machines. Inspired by centrifugal casting the metal powder is held on a circular track with high angular velocities causing a centrifugal acceleration of the particles in the powder bed, that overcomes gravitation. The laser optics is centered in the rotational axis melting the high velocity particles.

Process limitations are caused by the tradeoff between stabilized powder distribution and limited scanning speed. To increase processability and allow scalability the independent rotation of laser beam and powder bed were installed. This paper shows the development of a first prototype and initial process trials.

Additive Manufacturing (AM) has emerged as a more sustainable alternative to other conventional manufacturing processes (e.g. machining). In this study a real-time monitoring system is used to monitor the laser directed energy deposition (DED-LB/P) process by a high speed IR camera, and acquire the actual values of the processing parameters (laser power, processing speed, powder flow, carrier and shielding gas flows, robot TCP coordinates and orientation) and power consumption of the AM equipment (laser, robot, powder feeder, and other auxiliary equipment). This monitoring system allows to perform the optimization of the DED-LB/P process regarding component quality, material consumption, and energy efficiency. Different process parameters, path planning and manufacturing strategies to produce Ti6Al4V alloy parts are compared according to both quality acceptance criteria and sustainability performance indicators (energy consumption, carbon footprint, resource use). These sustainability performance indicators can be used to compare DED-LB/P process with other AM and conventional manufacturing technologies.