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.