Conference Agenda

Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).

Please note that all times are shown in the time zone of the conference. The current conference time is: 29th Jan 2022, 05:50:42am CET

Only Sessions at Location/Venue 
Program for LiM 2021
Location: Room 3
ICM Ground Floor 125
Date: Tuesday, 22/June/2021
10:00am - 11:00amMicro: Ablation 1
Location: Room 3
Session Chair: Johannes Heberle, Bayerisches Laserzentrum GmbH (blz), Germany
Room 3 
10:00am - 10:15am

Plasma dynamics induced by single-pulse femtosecond laser ablation of dielectrics and metals

Bruno Gonzalez-Izquierdo, Haruyuki Sakurai, Ryohei Yamada, Kuniaki Konishi, Makoto Kuwata-Gonokami, Junji Yumoto

The University of Tokyo, Japan

The generation of plasma is inherent to subtractive laser processing phenomena and often determines energy absorption and damage characteristics. However, few experimental studies have directly focused on quantitatively analyzing such laser-induced plasma dynamics. Here, shadowgraph and interferogram techniques were combined in a pump-probe configuration to investigate experimentally the temporal (from sub-ps to ns) and spatial dynamics of ablation plasma generated under single-pulse, ultrashort (90-400fs) laser ablation of sapphire and copper. From the measurements, we derived the electron-plasma density and plasma distribution for each time delay. The results clearly reveal time evolution differences between the materials. In sapphire, the plasma expands predominantly perpendicularly to the surface and attains higher electron-plasma densities. In copper, more shocked air-plasma is produced which, instead, expands uniformly. These results provide new insights into the underlying physics of laser-induced plasma dynamics which could facilitate, for instance, the optimization of recent high repetition rate configurations in laser processing.

10:15am - 10:30am

Ultrafast pump-probe microscopy reveals the influence of a water layer on the early stage ablation dynamics of gold

Maximilian Spellauge1,2, Carlos Doñate-Buendia2, Stephan Barcikowski2, Bilal Gökce2, Heinz P. Huber1

1Munich University of Applied Sciences, Department of Applied Sciences and Mechatronics, Lothstrasse 34, 80335 München, Germany; 2Universität Duisburg-Essen, Lehrstuhl für Technische Chemie I, Universitätsstrasse 7, 45141 Essen, Germany

Despite the tremendous amount of research carried out in the field of pulsed laser ablation in liquids, there are only a few works available regarding the early stage ablation dynamics. A description how the liquid influences ablation on time scales ranging from pico- to microseconds would give valuable information regarding the physical processes involved. In this work we report on ultrafast pump-probe microscopy measurements of a high purity bulk gold sample immersed in air and water. Our setup enables the observation of transient dynamics ranging from pulse impact on the picosecond timescale to shock wave and cavitation bubble propagation on the nanosecond to microsecond timescale. We find that the water layer significantly influences the ablation dynamics on the whole investigated temporal range.

10:30am - 10:45am

Advanced metal ablation based on highly flexible ultra-short pulsed laser platforms

Marc Sailer1, Axel Fehrenbacher1, Aleksander Budnicki1, Steffen Rübling2, Ulf Quentin2

1TRUMPF Laser GmbH, Germany; 2TRUMPF Laser und Systemtechnik GmbH, Germany

Considering the energy efficiency and the ablation quality, micromachining of several metals is examined for different processing regimes depending on timescales from fs to µs. Choosing an optimized temporal energy deposition can address a variety of machining aspects like ablation efficiency and surface morphologies. Using the unique features of the TRUMPF TruMicro series, the temporal energy deposition can be influenced during operation on a femto- up to a microsecond timescale by tuning parameters such as the ultrashort pulse duration or employing bursts in the MHz- and GHz-regime. This enhanced flexibility paired with patent-pending process strategies leads to cutting-edge processing speeds and surface qualities.

11:15am - 12:30pmMicro: Ablation 2
Location: Room 3
Session Chair: Stefanie Kohl, Institute of Photonic Technologies (LPT), Germany
Room 3 
11:15am - 11:30am

Laser ablation of thermoplastic composite for aerospace application

Hagen Dittmar, Simon Hirt, Verena Wippo, Peter Jaeschke, Stefan Kaierle, Ludger Overmeyer

Laser Zentrum Hannover e.V., Germany

Carbon fibre reinforced plastic (CFRP) is a well-established material in modern aerospace products. While primary structural components contain a thermoset matrix material, secondary components are increasingly made of thermoplastic matrix systems. Due to their superb performance and advantageous production properties, thermoplastics matrices are now also pushing into primary structural applications like fuselage, cowlings, and wings.

These structures are subject to an increased risk of damage during operation. Thus, repair strategies that address thermoplastic CFRP come to the fore. The repair by conventional tooling faces challenges that result from the thermoplastics’ abilities to melt, which cause the tools to clog and decrease process efficiency. Laser ablation poses an alternative approach allowing precise material removal without material related wear and thus a constant process quality.

This study demonstrates process efficiency of a laser ablation process on a CFRP with polyphenylene sulphide (PPS) matrix and the used processing parameters on the repair quality.

11:30am - 11:45am

Magnetic field assisted laser ablation of silicon by using short and ultrashort laser pulses

Yiyun Kang1, Garik Torosyan1, Falicienne G. Keabou1, Hicham Derouach1, Mareike Schäfer1, Pavel N. Terekhin2, Bärbel Rethfeld2, Johannes A. L'huillier1

1Photonik-Zentrum Kaiserslautern e.V. and Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany; 2Department of Physics and Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany

A controlled machining process with optimum energy-matter coupling in micro-scale by short and ultrashort laser pulses brings great benefits in industrial applications. The influence of external magnetic field on the ablation process of silicon irradiated by laser pulses in the infrared range was investigated. The external field is applied parallel to the laser beam to prevent escaping of the charge carriers in the laser-induced plasma plume from the ablation area. We performed single- and multi-pulse ablation in three different duration ranges: femtosecond, picosecond and nanosecond. We observed that the effect of external magnetic field depends strongly on pulse duration. An essential improvement in the quality and efficiency of material removal was achieved for pulses with longer durations. Additionally, by femtosecond excitation in multi-pulse mode a change of the surface texture around the ablation point was observed, which could be suppressed by means of the magnetic field.

11:45am - 12:00pm

Modeling of selective laser ablation of lithium-ion battery electrodes

Max-Jonathan Kleefoot1, Simon Ruck1, Jiří Martan2, Jens Sandherr1, Marius Bolsinger1, Volker Knoblauch1, Harald Riegel1

1Aalen University, Germany; 2University of West Bohemia, Czech Republic

Lithium-ion batteries are an important component of the current energy and mobility transition. Various approaches are being pursued in current research regarding the production of fast chargable electrodes. These electrode layers consist of various components that can be divided into two groups. One is the active material phase and the other is the binder material phase. In addition to laser perforation, selective laser ablation to remove inactive electrode components is also being investigated in research. Within this study, a model was developed that predicts the temperatures during the laser process inside the electrode at different depths. Experimental investigations were also able to show that the active material is permanently damaged by an excessively high energy input. A comparison with the model shows good agreement here. Thus, with the help of the model, a parameter optimisation can be carried out in which the active material particles are exposed but not damaged.

12:00pm - 12:15pm

Theoretical analysis of the incubation effect on the ablation behavior using spatial shaped ultra-short pulse laser

Marco Smarra1, Evgeny Gurevich2, Cemal Esen1, Andreas Ostendorf1

1Ruhr-Universität Bochum, Germany; 2Fachhochschule Münster, Germany

Ultra-short laser pulses are well known for their low thermal effect on the ablation process and therefore are used in numerous applications like surface texturing and functionalization. However, high peak fluence leads to a reduction in ablation efficiency. Beam shaping can be used to solve this issue. Beam errors, like defocus or astigmatism, lead to larger beam diameter and to decreasing peak fluence on the surface of the workpiece. This paper is focused on the theoretical study of the incubation effect and its influences on the ablated volume per pulse by analyzing the effects of the waist position of the laser beam and the ablation threshold of the sample material. This work is fundamental for handling the ablation process using high pulse energies.

12:15pm - 12:30pm

Expanding perspectives for processing with agile high power femtosecond lasers

Eric Audouard, Guillaume Bonamis, Martin Delaigue, Benoît Tropheme, Julien Pouysegur, Florent Basin, Jorge Sanabria, Eric Mottay, Clemens Honniger


300 W industrial laser is already available, and the mean power will reach soon the kW level. We are at a turning point in femtosecond technologies, which will enable new fields of use and new methods of production: The "agility" of the lasers and associated beam engineering make them relevant tools for flexible, reconfigurable production. We report on a versatile industrial high power femtosecond laser platform responding to the most demanding application requirements and opening the way to “macro” applications to femtosecond lasers. The platform generates femtosecond pulses at more than 300 W average power, the capability for efficient frequency conversion to 343 nm, free triggering of the laser output pulses, and burst generation and shaping over a wide range of parameters including GHz bursts.

1:30pm - 2:30pmMicro: System Technology and Process Control
Location: Room 3
Session Chair: Clemens Roider, Institute of Photonic Technologies (LPT), Germany
Room 3 
1:30pm - 1:45pm

Optical system for multi Bessel beam high power ultrashort pulsed laser processing using a spatial light modulator

Christian Lutz1, Simon Schwarz1, Stefan Rung1, Jan Marx2, Cemal Esen2, Ralf Hellmann1

1University of Applied Science Aschaffenburg, Germany; 2Ruhr University Bochum, Germany

We report on an optical setup for multi Bessel beam processing combining refractive axicon and spatial light modulator technology. Based on their particular beam profile, Bessel beams exhibit various advantages over conventional Gaussian beams for ultrashort pulsed laser processing. Especially for micromachining of transparent materials, applications like drilling micro-holes or the generation of voids benefit from the increased focal length of a Bessel beam. In addition, on account of the significantly increased average output power of industrial ultrashort pulsed lasers over the last years, there is a high demand on multi spot applications for using the available laser power in efficient production processes. Our optical concept combines the dynamic possibilities of beam splitting using spatial light modulator with the benefits of Bessel beams facilitating multi Bessel beam processing.

1:45pm - 2:00pm

Water jet guided laser as a versatile tool for industrial turning applications

Jehan Moingeon, Jeremie Diboine, Amedee Zryd, Bernold Richerzhagen

Synova SA, Switzerland

The Laser Microjet® technology couples a nanosecond pulsed Nd:YAG laser into a thin cylindrical water jet. It comes with numerous advantages such as a reduced heat affected zone and a parallel energy beam over several centimeters. Laser turning is in high demand to process hard or fragile materials allowing the production of complex solids of revolution. However, conventional laser must still contend with heat management, as well as the energy needed to ablate the whole volume. The LMJ technology can both cut-out large section in facets as well as fully turn the surface by ablation. Effective and efficient strategies of roughing and finishing become therefore possible and can yield high throughput. A surface roughness with Ra as low as 0.2µm can be reached. This paper presents several water jet guided laser turning strategies and their implementation in challenging industrial turning applications.

2:00pm - 2:15pm

Automated synthesis of colloidal nanoparticles powered by microchip lasers

Tobias Bessel, Sarah Dittrich, Bilal Gökce, Stephan Barcikowski, Friedrich Waag

Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Germany

Energy and health, two topics with continuing high relevance for our society, which require intensive R&D. Nanoparticles, with their unique properties, already make an important contribution to both fields and will play an even more essential role in the future. Access to high-quality nanoparticles for R&D is still difficult, especially when high purity and material diversity are required. Pure colloidal nanoparticles of numerous combinations of particle material and dispersion medium become available by pulsed laser ablation. Novel microchip lasers now enable the transfer of the synthesis method from the laser lab to any R&D lab as a compact, easy-to-use machine. The low-power lasers impress with unprecedented power efficiency in the laser synthesis of colloids. In addition, innovative solutions in measurement and control technology make full automation of the nanoparticle production possible.

2:15pm - 2:30pm

Mastering micro-filamentation for semiconductor-metal ultrafast laser welding

Maxime Chambonneau1, Qingfeng Li1, Vladimir Yu. Fedorov2, Markus Blothe1, Stelios Tzortzakis2, Stefan Nolte1,3

1Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Germany; 2Science Program, Texas A&M University at Qatar, Qatar; 3Fraunhofer Institute for Applied Optics and Precision Engineering IOF, Germany

While ultrafast laser welding is a proven technique for bonding a wide variety of materials together, it has no equivalent for semiconductor-metal, which would be particularly interesting for applications in microelectronics. We explain this nonexistence by the strong nonlinear propagation effects in the semiconductor. Nonlinear propagation imaging shows significant nonlinear focal shift values, in excellent agreement with self-focusing theory. We demonstrate that this nonlinear focal shift leads to a drastic depletion of the light intensity at the exit surface of silicon, at levels insufficient for laser welding applications. By determining and precompensating the nonlinear focal shift, the energy delivered at the interface is optimized, leading to the very first demonstration of semiconductor-metal laser welding. A maximum shear joining strength of 2.2 MPa is measured between the samples, which is compatible with applications. Ultimately, material analyses of the welds shed light on the underlying physical mechanisms.

2:45pm - 4:00pmMicro: Ablation 3
Location: Room 3
Session Chair: Moritz Späth, Institute of Photonic Technologies (LPT), Germany
Room 3 
2:45pm - 3:00pm

Comparison of ultrafast laser ablation of CrMnFeCoNi high entropy alloy to the conventional stainless steel AISI 304

David Redka1,4, Christian Gadelmeier2, Jan Winter1,3, Maximilian Spellauge1, Ján Minár4, Heinz P. Huber1

1Department of Applied Sciences and Mechatronics, Hochschule München University of Applied Sciences, Germany; 2Metals and Alloys, University of Bayreuth, Germany; 3Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universit¨at Erlangen-Nürnberg, Germany; 4New Technologies-Research Center, University of West Bohemia, Czech Republic

Ultrafast lasers as tools are nowadays mainly used in the field of high-precision laser micromachining. However, for technical applications, besides process optimization, the development of new functional materials is of crucial importance. In this work, we present a novel study on single-pulse laser ablation (530 fs, 1056 nm) of CrMnFeCoNi high entropy alloy (HEA), and compare results to the conventional stainless steel AISI 304. While HEAs are known to have a high damage resistance against high-energy particle radiation we find that this is not true for electromagnetic radiation, as the damage threshold of CrMnFeCoNi HEA is 0.24 J/cm2, which is lower than that of AISI 304 (0.27 J/cm2). A detailed analysis of the crater morphology, ablation depths as well as ablation volumes shows that the ablation mechanisms for both alloys are comparable, but contrary to expectations, CrMnFeCoNi HEA laser ablation is energetically more efficient in comparison to AISI 304.

3:00pm - 3:15pm

Electric field-assisted laser ablation of silicon in air by using ultrashort laser pulses

Yiyun Kang1, Garik Torosyan1, Hicham Derouach1, Mareike Schäfer1, Pavel N. Terekhin2, Bärbel Rethfeld2, Johannes A. L'huillier1

1Photonik-Zentrum Kaiserslautern e.V. and Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany; 2Department of Physics and Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany

Precisely processing on silicon, as widely used material in electronic devices, has shown a rising interest in laser micromachining. To optimize this process, we apply an external electric field parallel to the laser beam axis during irradiation of samples with ultrashort laser pulses. When the electric field is turned on, the free electrons and holes are redistributed within silicon due to electron drift. The electrons can be localized near the surface area which is supposed to influence the laser excitation process. Thus, the external electric field influences the absorption process due to the reorganized spatial distribution of electrons. We investigated the effect of an applied static strong electric field during single- and multi-pulse treatment of silicon. We observe an enhancement of ablation depth by applying the electric field in the direction of laser radiation.

3:15pm - 3:30pm

Influence of the build angle dependent surface quality on the ultra-short pulsed laser ablation of additive manufactured AlSi10Mg samples

Simon Ruck1,2, David K. Harrison2, Anjali De Silva2, Max-Jonathan Kleefoot1, Harald Riegel1

1Aalen University, Germany; 2Glasgow Caledonian University, United Kindom

Additive Manufacturing (AM) been proved as a method to offer new possibilities for the production of highly complex parts. One new interesting but yet small field of application is the 3D printing of complex optical elements, e.g. complex reflective mirror optics with integrated lightweight structures. However, to achieve surfaces with an optical quality on additive manufactured metal parts, mostly mechanical machining processes such as diamond turning or pad polishing are used. The studying of laser material processing, e.g. ultra-short pulsed laser ablation as a post-processing method for additive manufactured optical components is of great importance. In this study, we investigate the influence of the initial surface quality on the ultra-short pulsed laser ablation process. Therefore, we varied the build angles of our samples and used different laser parameter setups to determine e.g. the ablation rate, achievable surface quality and process efficiency.

Date: Wednesday, 23/June/2021
10:00am - 11:00amMicro: Ablation, Drilling and Cutting 1
Location: Room 3
Session Chair: Dr. Hans-Joachim Krauß, Bayerisches Laserzentrum GmbH, Germany
Room 3 
10:00am - 10:15am

Formation of smooth and flat area for monocrystalline diamond by ns pulsed laser

Yasuhiro Okamoto, Tubasa Okubo, Atsuya Kajitani, Akira Okada

Okayama University, Japan

The combination of ns pulsed laser and acid cleaning can achieve a smooth and flat surface below Ra=0.2 µm for monocrystalline diamond, when laser fluence is controlled around the threshold of removal. Although Gaussian mode is used, shiny and flat surface can be obtained in parallel direction to top surface of workpiece. Therefore, formation method of smooth and flat surface was experimentally investigated by repeating linear grooving, when ns pulsed laser of top-hat mode (1060 nm) was employed. However, subsequent linear grooving to previous one made it difficult to create flat surface with a constant depth, and two-step irradiation method was proposed. Non-removal areas were kept between processed lines in the first step, and the remained area between processed lines of the first step was removed in the second step. The two-step irradiation method was effective to achieve a wide flat-area, and it could improve the controllability of groove depth.

10:15am - 10:30am

Laser structuring of PVD multi-layer coatings for wear reduction

Andreas Stephen1, Bastian Lenz2, Andreas Mehner2, Tim Radel1

1BIAS GmbH, Germany; 2Leibniz-IWT, Germany

Surface texturing is an effective way of improving tribological properties. Its main effect mechanisms are to trap wear particles and store lubricants. One of these technologies is texturing the surface with micro dimples by laser ablation. In this paper, the selective texturing of multi-layer systems, i.e., removing only the top layer by ultra-short pulse laser processing is presented. The removal of the top layer with 1 µm in thickness of the systems (TiN/MoS2:Ti and TiN/a-C:H:Ti/MoS2:Ti:C) is proven by laser confocal microscopy and EDX analysis. The selective laser structuring of the multi-layer systems generated by PVD synthesis developed for tribological applications, among others for the aerospace industry, results in precise structures with depth deviations of less than 0.2 µm without burrs or melt residues. These textures will further on result in reduced wear depending on the structured layer systems and the geometry of the textures regarding dimple diameter and density.

10:30am - 10:45am

Optimized laser cutting processes and system solutions for separation of ultra-thin glass for OLED lighting and display applications

Rene Liebers, Mandy Gebhardt

3D-Micromac AG, Germany

For some years now, laser cutting processes based on filament technology with ultrashort pulse (USP) lasers have been increasingly adopted in industrial applications. The main reasons for this are the good edge quality that can be achieved with simultaneous easy automation and free-form capability. This ability to be automated is of critical importance, especially for applications that target the mass market with their end products. However, the real advantage of the technology comes from its almost unlimited free-form capability. In addition to established manufacturing processes for glasses of medium thickness from 0.2-2 mm, an increasing number of applications with ultra-thin glasses of 30-100 µm are entering the market. These applications also require further development of the process and fab technology.

This presentation covers the possibilities of laser technology based on applications for OLED-based lighting and glass components in the display area.

11:15am - 12:30pmMicro: Ablation, Drilling and Cutting 2
Location: Room 3
Session Chair: Lisa Ackermann, Institute of Photonic Technologies (LPT), Germany
Room 3 
11:15am - 11:30am

Polymer film processing with a high-power industrial femtosecond laser

Chandra Sekher Reddy Nathala, Victor Matylitsky, Herman Chui

MKS Spectra-Physics

Polymer materials are increasingly important for medical device, flat panel display and microelectronics applications. Due to the high thermal sensitivity of polymers, femtosecond laser processing can minimize heat deposition, and high powers are needed to achieve fast processing. In our work, we present ablation thresholds and cutting speeds for two common polymer materials, polyethylene terephthalate (PET) and polyimide, processed with a 100 W femtosecond laser with single and burst pulses and at infrared and green wavelengths. Cutting speeds were determined for both single-pass and multi-pass strategies. In addition to determining the ablation thresholds and the maximum cutting speed, the processed samples were analyzed for kerf width and heat affected zone (HAZ). The effect of burst mode operation and spot size on cutting speed, kerf width and HAZ were determined. With optimized parameters, high speed, high quality cutting of PET and polyimide films was demonstrated with a high-power femtosecond laser.

11:30am - 11:45am

Roll-to-roll laser processing of flexible devices

Maurice Clair, Christian Scholz, Mandy Gebhardt

3D-Micromac AG, Germany

In the manufacturing of flexible thin-film devices precision, throughput, and machining quality on ever-smaller structures are playing an important role.

The presentation will give a brief overview of different case studies where roll-to-roll (R2R) laser processing achieve new dimensions in terms of precision, quality and process efficiency.

An example application is the ablation of thin-film layers for medical sensors. In this case, the on-the-fly laser ablation takes place by using an excimer laser and mask projection. The layout of the products is adaptable by various projection masks. The high-repetition rate of the excimer laser allows the production of up to 150 sensors per second. Furthermore, thin-film annealing and cutting of metal substrates with ns lasers as well as thin-film patterning and cutting of polymer substrates with ultrashort pulse laser in a R2R process will be discussed.

11:45am - 12:00pm

Combining LPBF and ultrafast laser processing to produce parts with deep microstructures

Manuel Henn, Matthias Buser, Volkher Onuseit, Rudolf Weber, Thomas Graf

Institut für Strahlwerkzeuge IFSW, Germany

Laser Powder Bed Fusion (LPBF) is limited in the achievable accuracy, surface quality and structure size due to its inherent melting process. The achievable structure sizes are mainly dependent on the focal diameter and the grain size of the powder. Smaller structures, especially deep and narrow slits with a width below 100 µm, are still a major challenge.

Combining continuous wave and ultrashort pulsed lasers in the same optical system enables consecutive additive and subtractive processes. This results in a quasi-simultaneous manufacturing process, where the emerging part can be precisely machined with ultrafast laser ablation after each additively added layer.

In the talk the system technology used for the superposition of the lasers as well as the results of the combined additive and subtractive processes for the fabrication of deep and narrow slits in stainless steel parts will be shown.

12:00pm - 12:15pm

Towards in situ monitoring and feedback control of femtosecond laser-induced nanogratings formation in dielectrics

Olivier Bernard1, Andrea Kraxner2, Assim Boukhayma2,3, Ata Golparvar2, Yves Bellouard1, Christian Enz2

1Galatea Lab, École polytechnique fédérale de Lausanne, Rue de la Maladière 71b, CH-2002 Neuchâtel, Switzerland; 2Integrated Circuits Laboratory, École polytechnique fédérale de Lausanne, Rue de la Maladière 71b, CH-2002 Neuchâtel, Switzerland; 3Senbiosys SA, Rue de la Maladière 71c, CH-2000 Neuchâtel, Switzerland

Tightly focused non-ablative femtosecond laser pulses induce a variety of structural modifications in the bulk of dielectrics. Among those, sub-wavelength nanogratings are particularly interesting as a means not only to locally enhance the material etching selectively (and thus, enabling bulk 3D-micro-fabrication), but also for encoding rich information in high-density permanent data storage media. Femtosecond laser-based processes are subject to perturbations, affecting the repeatability and accuracy of the results. To increase the performance of these processes, we explore a feedback method based on direct monitoring of the laser-affected zone (LAZ) using a probe beam. Specifically, we report on the use of weak signals resulting from the interaction of a femtosecond laser probe-beam with the nanogratings index-modulation as objective functions in feedback loop algorithms.

1:30pm - 2:30pmMicro: Drilling
Location: Room 3
Session Chair: Dr. Florian Klämpfl, Institute of Photonic Technologies (LPT), Germany
Room 3 
1:30pm - 1:45pm

Experimental investigations of a helical laser drilling process for pilot holes on complex surfaces

Sebastian Michel, Pascal Volke, Dirk Biermann

Institute of Machining Technology (ISF), Technical University Dortmund, Germany

Increasing requirements and a high degree of freedom in design increasingly demand the manufacturing of bore holes with small diameters and high length-to-diameter ratios on complex shaped surfaces. Injection nozzles, medical tools and implants, cooling holes or oil channels are just a few examples. Unlike mechanical drilling tools, the laser beam is not deflected on inclined or curved surfaces and can therefore be used to create pilot holes for a subsequent mechanical drilling process. In this paper, the generation of pilot holes on flat and inclined surfaces using a Nd:YAG laser is investigated. A helical laser drilling process is used to drill holes with a diameter of 1.5 mm in X2CrNiMo17-12-2 stainless steel. Hole depth, diameter, roundness, conicity and material influences are evaluated. Application tests with single-lip drilling tools prove the potential of the laser holes to serve as a drilling guide for the mechanical deep hole drilling process.

1:45pm - 2:00pm

Laser microdrilling of thin aluminium sheets for metal-composite adhesion promotion

Félix Ares1, Ivette Coto1, Tamara Delgado1, Francisco Gontad1, Laura Mera1, Pablo Romero1, Sara Vidal1, Pascal Massé2, Nerea Otero1

1AIMEN, Spain; 2Rescoll, Société de Recherche, France

Thin (200 µm) aluminum sheets were drilled using a 1070 nm, CW fiber laser to improve hybrid metal-composite adhesion. The laser beam was guided by a BEO D35 laser cutting head. Micro holes of several diameters (40 – 220 µm) were generated with different spacing among them. The aluminum sheets were later coated with an adhesion promotion spray and thermoformed with a thin (200 µm) Carbon Fiber Reinforced Polymer (PA66) tape. InterLaminar Shear Strength (ILSS) and Single Lap Joint (SLJ) tests were performed on the following thermoformed samples: 1) Drilled, uncoated samples, 2) Non-drilled, coated samples, 3) Drilled, coated samples. The results show that a significant adhesion improvement for the drilled, coated aluminum samples is accomplished, reaching up to 100% higher apparent interlaminar shear strength than plain, coated samples. Finally, the pattern that provided the best ILSS values was replicated with a ns pulsed fiber laser, resulting in an equally strong bonding, while increasing productivity tenfold.

2:00pm - 2:15pm

Fluence dependence of the edge quality of microhole exits for percussion drilling with ultrashort laser pulses

Anne Feuer, Rudolf Weber, Thomas Graf

IFSW, University of Stuttgart, Germany

For many applications, edge quality and shape accuracy of microholes are crucial. One assumption is that the fluence at the tip of the microhole during drilling is a key parameter for the quality of the microhole’s exit. It was therefore investigated experimentally how the fluence affects the edge quality. The experiments were performed in 0.5 mm thick steel using a Ti:Sapphire laser system operating at a wavelength of 800 nm, a pulse duration of 1 ps, and a repetition rate of 1 kHz. For the quantitative analysis of the edge quality, microscope images were evaluated using a machine learning approach. Two key figures, groove size and perimeter ratio, were defined that proved to be significant in characterizing the edge quality of exits. In the current talk it will be shown that the quality of exits of percussion-drilled microholes could be significantly improved if the fluence dependence is considered.

2:15pm - 2:30pm

High-speed offline and real-time monitoring and control for laser micro-drilling of large Ti sheets

Roberto Ocaña, Joseba Esmoris, Carlos Soriano

TeknikerTekniker-Basque Research & Technology Alliance, Spain

High-throughput laser micro-drilling is a highly demanded technology for several applications, including making filters, creating surfaces with better aerodynamic performance, etc. However, it is usually found that the sensitivity of the laser process to small deviations is quite high. That is why, while parameterizing, it is convenient to have techniques that allow us to monitor and control the process to ensure reproducible results. For this, we have developed several methods that combine monitoring and control in real-time and offline. For real-time control and monitoring, we have used optical coherence tomography and captured the scattered laser radiation during the process by means of photodiodes. Regarding offline monitoring, a procedure using a high-speed camera and an algorithm for measuring the dimensions of the microholes provides us the quality characteristics and statistical information of complete micro-perforated Ti sheets. Both methods work as fast as the laser process, i.e., 300 holes per second.

2:45pm - 4:00pmMicro: Micro Machining
Location: Room 3
Session Chair: Oliver Hentschel, Institute of Photonic Technologies (LPT), Germany
Room 3 
2:45pm - 3:00pm

Laser machining of different steel grades with 10ps laser pulses: the influence of carbides onto the surface roughness and structures for different laser parameters

Stefan M. Remund, Severin N. Herren, Josef Zürcher, Beat Neuenschwander

Berner Fachhochschule Technik und Informatik, Switzerland

When steel is machined with ultra-short pulses the specific removal rate strongly depends on the pulse fluence, the wavelength and, in case of bursts, on the number of pulses whereas the steel grade has a minor influence. This situation changes for the surface roughness. Beside the laser parameters, the initial surface and the number of machined layers the obtainable surface roughness also depends on the carbides located in the steel as well as their size and distribution and therefore it is strongly influenced by the steel grade. E.g. for a given set of parameters a surface roughness (sq) value of 350nm, 410nm and 500nm was achieved for CK75 (no carbides), M390 (small carbides) and K100 (large carbides). We will present the results of a systematic study for different steel grades in the application of surface structuring and smoothening of surfaces machined by alternative technologies as e.g. electrical discharge machining (EDM).

3:00pm - 3:15pm

Scaling the throughput of high-quality silicon laser micromachining using a 1-kW sub-picosecond laser

Daniel Holder1, Rudolf Weber1, Christoph Röcker1, Gerhard Kunz2, David Bruneel3, Martin Delaigue4, Thomas Graf1, Marwan Abdou Ahmed1

1IFSW, University of Stuttgart, Germany; 2Robert Bosch GmbH, Germany; 3Lasea, Belgium; 4Amplitude Systemes, France

Recently, laser processing of silicon with ultrafast lasers has gained widespread attention for manufacturing of optics for THz radiation, an emerging topic with applications in medical imaging, security and communication. Such THz-optics require high-quality surfaces with low roughness in order to provide high transmission and low scattering. In the past, the low average power of ultrafast lasers limited the achievable throughput in silicon laser micromachining.

In this work a processing strategy for high-quality high-throughput micromachining of silicon with a 1-kW sub-picosecond laser is presented, which takes benefit of pulse bursts, low fluences and high feed rates.

As a result, laser micromachining could be demonstrated as a suitable technology for manufacturing of smooth structures on silicon while maintaining a high throughput. Surfaces with an appropriate roughness of Sa ≤ 0.6 µm were produced with a high material removal rate of 230 mm³/min and a machining depth of up to 313 µm.

3:15pm - 3:30pm

Ultra-short laser micro-machining by spatially shaped ps- and fs-pulses for depth-selective µ-TLM resistivity test structures in TCO contact layers

Stephan Krause1,2, Stefan Lange2, Gao Yiding2, Volker Naumann2, Christian Hagendorf2, Paul-Tiberiu Miclea1,2

1Fraunhofer CSP, Germany; 2Martin-Luther-University Halle/Wittenberg

We applied spatially shaped ultra-short pulse laser micro-machining for a new processing approach of µ-TLM test structures. These structures are used for resistivity measurements of multilayer systems with highly resistive interface layers, e.g. in TCO top contacts for solar cells. For precise measurements of the electrical sheet and contact resistivity of the individual layers, isolating trenches and homogenous ablation areas are required that can be fabricated by matching of pulse overlapping based on rectangular spots in µm-dimensions.

Ultrashort pulses by 10 ps and 200 fs (515/532/1030 nm) as well as optical beam shaping elements for redistribution to top-hat intensity profiles enables a selective removal of the top TCO. Thus, thermal damage is minimized in the underlying material and multilayer adjacent region of the laser trenches by ultrafast ablation mechanism. Morphology and microstructure of heat-affected zones were characterized by high-resolution transmission electron microscopy to optimize laser recipes for enhancing ablation selectivity.

3:30pm - 3:45pm

Automated cutting by water jet-guided laser machining using a break-through sensor

Falk Braunmüller, Jérémie Diboine, Amédée Zryd, Bernold Richerzhagen

Synova S.A., Switzerland

The Laser Micro-Jet® is now a well-established technology among others for micro-machining and high-quality machining of hard and composite materials, with the advantages of narrow parallel cut walls without focus adaptation, minimizing the heat-affected zone and the avoidance of burrs.
This contribution describes the development of a break-through sensor measuring light from the laser plasma through the water jet. By detecting a completed cut, additional safety cutting passes can be reduced and the cutting is stopped just in time.
The sensor enables an optimized, automatized cutting, which represents a significant step towards industry 4.0. The technology is now employed on an industrial scale by several customers, showing the high potential of the technology: The processing time is reduced by 5-20%.
Finally, first results of a cutting sensor with spectrally resolved plasma detection will be presented, which shall enable a targeted ablation by detecting various layers in a multi-layer material.

3:45pm - 4:00pm

Laser turning using ultra-short laser pulses and intensity distribution techniques

Julian Zettl1, Christian Bischoff2,3, Stefan Rung1, Cemal Esen3, Andrés Fabián Lasagni4, Ralf Hellmann1

1University of Applied Sciences Aschaffenburg, Germany; 2Topag Lasertechnik GmbH, Germany; 3Ruhr University Bochum, Germany; 4Technical University Dresden, Germany

We report on the fabrication of rotationally symmetric parts by using focused ultra-short laser pulses while impinging the rotating work piece tangentially. The use of ultra-short laser pulses enables this process to fabricate parts in a non-contact manner, even from materials that are hard to machine such as stellite or fused silica. The target geometry is realized by moving the constantly rotating specimen according to the specified geometry under the focused laser spot. In order to further enhance this manufacturing approach, a spatial distribution of the laser power on the work piece is investigated. Beam shaping techniques are applied to alter the shape of the focal spot and to study the effects on the resulting ablation rate, process efficiency and surface quality.

Date: Thursday, 24/June/2021
10:00am - 11:00amAdditive Manufacturing: Medical Applications
Location: Room 3
Session Chair: Dr. Florian Klämpfl, Institute of Photonic Technologies (LPT), Germany
Room 3 
10:00am - 10:30am

Invited Talk: Selective laser sintering 3D printing of bespoke medications

Atheer Awad

University College London, United Kingdom

3D printing is a rapid manufacturing technology that has found promising applications in many fields, including pharmacy. In particular, laser-based technologies enable the creation of precise and intricate structures, potentially causing a paradigm shift in medicine design, manufacture and use. As an example, early-phase drug development (such as preclinical studies and first-in-human trials) could be expedited by using these technologies to rapidly produce formulations with excellent dose flexibility at low cost, on demand. Similarly, they could support formulation development because they have the capability to produce rapid product iterations for testing, such as excipient compatibility and drug release. Within hospitals and pharmacies, such technologies could accelerate the field of personalised medicine by moving treatment away from a ‘one size fits all approach’ towards personalisation. This presentation will give an overview on the use of a laser-based 3D printing technology and its promising applications, highlighting its potential in personalising medications.

10:30am - 10:45am

Laser directed energy deposition produces improved cp Ti for dental prosthetic applications

Óscar Barro1,2, Felipe Arias-González3, Fernando Lusquiños1,5, Rafael Comesaña4, Jesús del Val1, Antonio Riveiro4, Aida Badaoui4, Félix Gómez-Baño2, Juan Pou1,5

1CINTECX, University of Vigo, LaserON Research Group, Vigo, SPAIN; 2Corus-Fegoba, A Coruña, SPAIN; 3School of Dentistry, Universitat Internacional de Catalunya, Barcelona, SPAIN; 4Materials Engineering, Applied Mechanics and Construction Department, University of Vigo, Vigo, SPAIN; 5Galicia Sur Health Research Institute (IIS Galicia Sur), SERGAS-UVIGO, Vigo, SPAINin

Titanium and titanium alloys are widely employed in biomedical applications by virtue of their remarkable corrosion resistance, biocompatibility, exceptional specific strength and relatively low elastic modulus. Commercially pure titanium (cp-Ti) is a designation for titanium with reduced content of alloying elements, having a great resistance to corrosion and reduced cytotoxicity.

Laser directed energy deposition (LDED) is an additive manufacturing method able to produce metallic materials of great quality. By controlling the cooling rates, the material microstructure can be tuned in order to improve its mechanical/chemical properties. In the present work, LDED using a high power diode laser as energy source, was used to produce cp-Ti parts of grade 4. The cp-Ti obtained by LDED showed a higher mechanical performance than the commercial counterpart: 7% increment of ultimate tensile strength and 30% increment of toughness. These results can be attributed to a specific microstructure modification inherent to the LDED process.

10:45am - 11:00am

Additive manufacturing for minimally invasive endomicroscopy

Robert Kuschmierz, Elias Scharf, Jürgen Czarske

TU Dresden, Germany

Miniaturized flexible endoscopes employ coherent fiber bundles (CFB) to transfer intensity information by using lenses. This increases the footprint of the endoscope to several millimeters. Furthermore, the phase information of the light is distorted during transfer due to manufacturing errors of the CFB, which limits the endoscope to 2D imaging. Calibrating and compensating the phase distortion allows for lens less imaging. We present, the use of additive manufacturing to apply diffractive optical elements (DOE) onto the fiber facet for phase compensation. Using 2P-polymerization axial resolutions better than 20 nm can be achieved. This enables robust and cost efficient, endoscopes for 3D imaging. The influence of the DOE quality especially the axial resolution towards the image quality is discussed. With a total diameter below 400 µm, novel applications for instance for in-vivo cancer diagnostics in the brain can be envisioned.

11:15am - 12:30pmMicro: Innovations
Location: Room 3
Session Chair: Prof. Michael Schmidt, Institute of Photonic Technologies (LPT), Germany
Room 3 
11:15am - 11:45am

Invited Talk: Ultrashort pulsed laser micro processing: Multi-pulse and beam forming strategies for high throughput at high average powers

Beat Neuenschwander, Stefan M. Remund, Markus Gafner, Michalina W. Chaja

Bern University of Applied Sciences, Switzerland

The development of ultrashort pulsed laser systems actually goes far beyond the kW level. But e.g. for metals and single pulses todays standard methods like galvo scanners are not suited for higher average powers and alternative approaches have to be developed. We will get an insight into actual developments using multi-pulse strategies in temporal representation as pulse bursts and in spatial representation as multi-beams or with direct beam forming. A combination of these methods with synchronized scanning or real pulse on demand option could pave the way for using high average powers.

11:45am - 12:00pm

Excimer laser sintering of ceramic thin films for solid state batteries

Matthias Trenn1, Ralph Delmdahl2, Karsten Lange1

1Fraunhofer Institut für Lasertechnik ILT, Germany; 2Coherent LaserSystems GmbH & Co. KG, Göttingen

The geopolitical dependence on limited fossil resources and the increasing number of environmental disasters are enormous challenges for today’s society. An important element to overcome these essential problems is to increase the performance of energy storage systems and the efficiency of energy conversion devices. Promising solutions are solid state batteries and solid oxide fuel cells. Both cell systems demanding high standards on new production technologies. Temperature-sensitive thin film systems make conventional sintering processes impossible.
In the underlying investigation, a new highly scalable excimer laser-based sintering process of ceramic thin films is presented. The nanosecond pulses selectively melt surface the powder grains. Due to the 248 nm wavelength of the excimer laser, sintering depths of 3 - 8 µm can be achieved. In the process, the crystalline phase and thus also the electrochemical properties of the material are retained.

12:00pm - 12:15pm

Laser-based 3D-magnetic field sensor formation

Markus Müller, Mandy Gebhardt

3D-Micromac AG, Germany

A world with intelligent electronic devices in every machine and every pocket needs a wide range of sensor technologies. One rapidly growing technology is the sensing of magnetic fields, which can be used in numerous industrial applications. Very sensitive magnetic sensor chips can be realized by using GMR or TMR (Giant or Tunneling magnetoresistance) sensors in a Wheatstone bridge circuit built in a monolithic design.

This presentation gives an overview to selective laser annealing for 3D-magnetic field sensor formation, which provides several advantages over thermal annealing for magnetic sensor manufacturing. Its higher precision enables processing of smaller magnetic device structures, which in turn leads to more devices per wafer. In addition, its ability to set different reference magnetization directions on sensors across a single wafer reduces process steps and simplifies the manufacturing flow, enabling more cost-effective production of integrated monolithic sensor packages.

12:15pm - 12:30pm

Top-hat profile beam to weld polymeric microfluidics chips with ultra-short pulsed laser

Marc Décultot1, Jérôme Patars1, Anne Henrottin1, José Antonio Ramos-de-Campos1, Ivan Gusachenko2, Clément Jacquard2, Guillaume Labroille2, Gwenn Pallier2

1Lasea, Belgium; 2Cailabs, France

The microfluidics field, due to its various possibilities in the study of chemical and biological reactions with only few consumables, is expanding significantly. To follow this growing, we have developed a flexible solution, based on ultra-short pulsed laser technology, to engrave different microfluidic channels on a chip, and to seal them with a complete, hermetical, and resistant welding.

In order to improve the competitiveness of our solution for industrial production purpose, we have focused in particular our work on the improvement of the welding’s speed. Using the Canunda-Pulse solutions from Cailabs for manipulating high-power femtosecond lasers, we have made a complete study on laser welding parameters with a top-hat profile beam. Canunda-Pulse is a fully reflective passive optical module based on the Multi-Plane Light Conversion (MPLC) technology. Thanks to this beam shaper, we have deduced advantages of a top-hat profile beam, compared to a gaussian profile beam.

1:30pm - 2:30pmMicro: Processing of Transparent Materials 1
Location: Room 3
Session Chair: Dr. Thomas Stichel, Bayerisches Laserzentrum GmbH (blz), Germany
Room 3 
1:30pm - 1:45pm

Micromachining of transparent biocompatible polymers used as vision implants with bursts of femtosecond laser pulses

Simas Butkus, Evaldas Kažukauskas, Vytautas Jukna, Domas Paipulas, Valdas Sirutkaitis

Laser Research Center, Vilnius University, Lithuania

Biocompatible plastics are used for many different purposes (catheters, artificial heart components, dentistry products, etc.). An important field biocompatible polymers is the production of vision implants known as intraocular lenses (IOLs) or custom-shape contact lenses, which are typically produced by means of milling, turning or lathe cutting and subsequent polishing. The multiple-step process is expensive and may take up days to produce the final part which is individually customized to meet the patient's needs.

In this work we propose a novel, all-laser-based method for the production of custom-shape lenses which may work as eye-implants. The shape of the lens from the plastic material (Contamac CONTAFLEX 26% UV-IOL) is produced by means of femtosecond ablation in a few minutes and afterwards it is polished by utilizing burst of femtosecond pulses in the GHz regime. In this way, transparent optical-quality lenses are produced in under 5 minutes of laser fabrication.

1:45pm - 2:00pm

Solvent evaporation and annealing of solution-processed organic materials by laser irradiation on flexible substrates

Frederik Kiel1, Cemal Esen1, Andreas Ostendorf1, Volker Wirth2

1Ruhr-Universität Bochum, Germany; 2Focuslight LIMO GmbH, Bookenburgweg 4-8, 44319 Dortmund, Germany

The market for flexible, printed and organic electronics is rapidly growing. The production is often based on wet-chemical processes and the residual solvent needs to be removed. Conventional methods for solvent evaporation or annealing of functional layers in roll-to-roll (R2R-) processing are circulating-air- or infrared-dryers. These methods require a relatively large drying section and entail a long exposure time at elevated temperatures for the flexible substrates. By utilizing a diode-laser as heating source the installation space and especially the exposure time at elevated temperatures could be minimized.

A LIMO line laser system (450 W, 980 nm) was used to investigate the substitution of conventional drying/ annealing methods on a lab scale (laser line FWHM: 12,22x0,06 mm²) for organic photovoltaic cells resulting in comparable power conversion efficiencies to conventional methods at processing speeds of 1m/min.

These results are expected to be transferred from the lab scale to a R2R-system.

2:00pm - 2:15pm

Processing and wetting behavior of microstructured polymer foils

Felix Bouchard1, Marcos Soldera2, Robert Baumann1, Andrés-Fabián Lasagni1,3

1Technische Universität Dresden, Institut für Fertigungstechnik, George-Baehr-Str. 3c, 01069 Dresden, Germany; 2PROBIEN-CONICET, Dto. de Electrotecnia, Universidad Nacional del Comahue, Buenos Aires 1400, Neuquén 8300, Argentina; 3Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS), Winterbergstraße 28, 01277 Dresden, Germany

The demand for surface functionalized plastics is constantly rising. Therefore, industrial-scalable methods capable to provide surfaces with new functions are necessary. In this study, we demonstrate a strategy to apply hierarchical microstructures to transparent polyethlyene therepthalate (PET) foils by plate to plate hot embossing. To that end, a stainless steel stamp was patterned using two laser based processes, namely Direct Laser Writing (DLW) and Direct Laser Interference Patterning (DLIP). Several single scale and multi scale structures with feature sizes in the range 3 µm up to 50 µm and depths between 0.1 µm and 10 µm were processed on the metal master and transfered to the PET surface. The topography characterization by confocal microscopy and scanning electron microscopy revealed a satisfactory replication of the micostructures from the stamp to the polymer, even for the smallest features with lateral sizes of ~100 nm. The patterned surfaces showed an increased hydrophobic behavior characterized by static water contact angles up to 105°.

2:15pm - 2:30pm

Femtosecond laser-assisted mould fabrication for metal casting at the micro-scale

Enrico Casamenti1, Luciano Borasi2, Adeline Durand2, Samuel Rey1, Raphaël Charvet2, Cyril Dénéreaz2, Andreas Mortensen2, Yves Bellouard1

1Galatea Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland; 2Laboratory of Mechanical Metallurgy (LMM), École Polytechnique Fédérale de Lausanne (EPFL), Switzerland

Existing technologies for the production of metallic 3D micro-components are, in their current state, either too slow to be economically viable or produce porous and imperfect metal structures. Here we overcome those barriers by bringing metal casting to the realm of microfabrication. We present a process that enables the production of freeform, dense, 3D metal architectures at speeds well above alternative approaches for metal 3D printing at the same resolution. Using femtosecond laser micro-machining combined with chemical etching, arbitrarily shaped 3D-cavities are carved out of fused quartz substrates and subsequently pressure-infiltrated with high melting point metals, such as pure silver, copper and gold and their alloys. The resulting glass/metal combinations contain interconnected dense metal 3D structures that are shaped freely with micrometric resolution to enable new types of micro-devices and composite structures.

2:45pm - 4:00pmMicro: Processing of Transparent Materials 2
Location: Room 3
Session Chair: Dr. Kristian Cvecek, Institute of Photonic Technologies (LPT), Germany
Room 3 
2:45pm - 3:00pm

Deep engraving of fused silica glass using bursts of femtosecond pulses with intra-burst frequencies in the range of 25 - 100 GHz

Simas Butkus1,2, Martynas Barkauskas1,2, Aurimas Augus1, Martynas Kojelis1, Jonas Pocius1, Linas Giniūnas1

1Light Conversion, Lithuania; 2Laser Research Center, Vilnius University, Lithuania

Due to the high precision offered by ultrashort pulse micromachining, femtosecond laser systems are applied in both industrial and scientific fields. To accompany the needs of the industry, a trend towards high average power (>100 W) femtosecond laser systems for micromachining has become apparent. However, upscaling the micromachining throughput is not straightforward and typically results in a decrease in the micromachining quality. To this end, new ideas are sought to increase the efficiency of an ablation-based process.

In this work we present data on deep engraving of fused silica glass using burst of femtosecond pulses with a custom-built laser capable of tuning the intra-burst temporal gap producing a variable effective repetition rate of 25 – 100 GHz. By adjusting the average power, number of sub-pulses within the burst and the intra-burst gap it was found that the ablation efficiency can be increased by several-fold as compared to the convention single-pulse regime.

3:00pm - 3:15pm

Fully reflective Bessel beam generation with constant energy distribution over the propagation axis for complex glass cutting

Siddharth Sivankutty, Antonin Billaud, Gwenn Pallier, Pu Jian, Olivier Pinel, Guillaume Labroille

Cailabs, France

Glass cutting with femtosecond lasers is spreading led by the touch panel displays development. Bessel beams are very efficient and precise way to process glass thanks to their extended depth of focus 100 times longer than a standard Gaussian beam and their central beam which can be smaller than the diffraction limit.

High quality glass cutting with a reflective axicon has already been demonstrated with no oscillations leading to cleaner cuts and faster processes. The beam is able to propagate through a galvo-scanner and a F-theta lens. The reflective design is compatible with extreme high peak and average power.

Here we describe the generation of a complex Bessel beam profile flatter over the propagation axis based on a reflective design. The tail of this profile is five times sharper compared to standard Bessel beams paving the way to complex glass cutting such as multi-layer glasses.

3:15pm - 3:30pm

Optical coherence tomography for 3D weld seam localization in absorber-free laser transmission welding

Frederik Maiwald1, Clemens Roider2, Michael Schmidt2,3, Stefan Hierl1

1Ostbayerische Technische Hochschule Regensburg, Labor Lasermaterialbearbeitung, Technologie Campus Parsberg-Lupburg, Am Campus 1, 92331 Parsberg, Germany; 2Institute of Photonic Technologies, Friedrich-Alexander-Universität Erlangen-Nürnberg, Konrad-Zuse-Straße 3/5, 91052 Erlangen, Germany; 3Erlangen Graduate School in Advanced Optical Technologies (SAOT), Paul-Gordan-Str. 6, 91052 Erlangen, Germany

Thulium fibre lasers emit in the intrinsic absorption spectrum of polymers and enable welding of transparent parts without absorbent additives. Focusing with high NA provides large intensity gradients inside the workpiece, enabling selective fusing of the joining zone without affecting the surface. Therefore, absorber-free laser transmission welding is well suited to fulfil the high demands on quality and reliability in manufacturing of optical and medical devices. However, monitoring the welding process is required, since seam size and position are crucial for quality.

The aim of this work is the volumetric acquisition of the weld seam’s location and size using optical coherence tomography. Due to the change of the optical properties during melting, the seam can be distinguished from the base material. The results coincide with microscopic images of microtome sections and demonstrate that weld seam localization in polyamide 6 is possible with an accuracy better than a tenth of a millimetre.

3:30pm - 3:45pm

Laser-manufactured glass microfluidic devices with embedded sensors

Krystian L. Wlodarczyk1,2, William N. MacPherson2, Duncan P. Hand2, M. Mercedes Maroto-Valer1

1Research Centre for Carbon Solutions, School of Engineering and Physical Sciences, Heriot-Watt University, Riccarton, Edinburgh, EH14 4AS, UK; 2Applied Optics and Photonics group, School of Engineering and Physical Sciences, Heriot-Watt University, Riccarton, Edinburgh, EH14 4AS, UK

Recently, we have developed a laser process that enables the rapid fabrication of microfluidic devices using widely-available borosilicate glass slides. In contrast to conventional manufacturing techniques, there is no requirement for projection masks and hazardous glass etchants, such as hydrofluoric acid. Instead, a single item of equipment, i.e. an ultrashort pulsed picosecond laser (Trumpf TruMicro 5x50), is used to: (a) write microfluidic patterns directly onto the glass surface by ablating the material and (b) permanently enclose the microfluidic structure from the top by welding this glass substrate to another glass slide that typically contains inlet/outlet ports. In this work, we demonstrate that this process also allows us to manufacture customised glass microfluidic devices with embedded sensors, which enable local, real-time monitoring of various parameters, such as pressure and pH, inside the microfluidic patterns.

3:45pm - 4:00pm

Ultrashort pulse laser cutting of colorless polyimide and hard coat film stacks for flexible OLED displays

Jim Bovatsek, Terence Hollister

MKS Spectra-Physics, United States of America

New mobile devices include flexible and foldable OLED displays which require new protective cover materials. Options for this include ultrathin glass (UTG) as well as a new type of colorless polyimide (CPI), which is transparent at visible wavelengths. The CPI is combined with a scratch resistant hard coat (HC) layer and a final PET (polyethylene terephthalate) protective film. Here we present results for cutting thick CPI/HC/PET layered stacks using high power UV ultrashort pulse lasers. Ablation thresholds were found to vary by almost a factor of ten, and a layer-optimized cutting approach was used. The optimized cutting process is of high quality and throughput, with heat-affect zone (HAZ) of <10 µm and cutting speed of >400 mm/s. These results are comparable to that for individual sheets of polymers used in OLED display manufacturing.


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