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.