Extending ultra-short pulse laser texturing over large area

Abstract

Surface texturing by Ultra-Short Pulses Laser (UPL) for industrial applications passes through the use of both fast beam scanning systems and high repetition rate, high average power P, UPL. Nevertheless unwanted thermal effects are expected when P exceeds some tens of W. An interesting strategy for a reliable heat management would consists in texturing with a low fluence values (slightly higher than the ablation threshold) and utilising a Polygon Scanner Heads delivering laser pulses with unrepeated speed.Here we show for the first time that with relatively low fluence it is possible over stainless steel, to obtain surface texturing by utilising a 2MHz femtosecond laser jointly with a polygonal scanner head in a relatively low fluence regime (0.11Jcm−2). Different surface textures (Ripples, micro grooves and spikes) can be obtained varying the scan speed from 90ms−1 to 25ms−1. In particular, spikes formation process has been shown and optimised at 25ms−1 and a full morphology characterization by SEM has been carried out. Reflectance measurements with integrating sphere are presented to compare reference surface with high scan rate textures. In the best case we show a black surface with reflectance value<5%.