High-Contrast Marking of Stainless-Steel Using Bursts of Femtosecond Laser Pulses.

The marking and surface structuring of various materials is important in various industrial fields such as biomaterials, luxury goods, anti-counterfeiting, automotive and aerospace, electronics and semiconductor industries, and others. Recent advances in laser technology, such as burst-mode lasers, have opened new ways of affecting the surfaces of various materials, inducing a different appearance and/or properties of the laser-exposed areas. From earlier studies, it is known that when splitting a single pulse into multiple pulses and thus creating a quasi-MHz-GHz repetition rate regime, it is possible to increase not only the ablation efficiency but it also provides the possibility to tune the heat in-flow into the surface. Such new regimes enable the control of the surface roughness as well as the optical properties and corrosion resistance. In this work, we analyze the effect of the different burst-mode regimes for the marking of stainless-steel samples, aiming to produce high-contrast marking having different shades of black/white color (black-gray-white). Moreover, we investigate the angular dependence of the reflected light after laser treatment numerically from the measured surface morphology.