ADVANCES IN UNDERSTANDING HOW FEMTOSECOND LASER RIPPLES FORMATION IN METAL WORKS

International audienceWe report advances in understanding how femtosecond laser ripples formation in metal works. The surface topology features are discussed in terms of periodicity and contrast of the pattern formation, related to chronological laser-induced events. Resonant excitation of Surface Plasmons (SP) in metallic gratings show that SP wave excited during the femtosecond laser pulse can initiate the observed patterning and play a key role. Metals behavior under nonequilibrium conditions on the picosecond timescale is then investigated to correlate the amount of material experiencing solid-to-liquid transitions and the subsequent ripples contrast. With the de-rived observation, a calculation of the transient nonequilibrium thermodynamic characteristics of excited nickel is also performed allowing defining characteristic timescales of thermocapillary proc-ess which may occur under multi- pulse irradiation