Femtosecond pulse laser ablation of chromium: experimental results and two-temperature model simulations

In this work, the results of experimental and computational single-and multi-shot ablation threshold and the incubation effect of chromium metal sample, irradiated by ultrashort laser pulses, are presented. The experimental value of the ablation threshold is determined based on D-2 method by measuring the outer ablation crater diameters as a function of incident laser pulse energy using 800 nm; 30 fs; laser pulses. The value of 0.19 +/- 0.04 (J/cm(2)), is obtained for the single-shot ablation threshold fluence. The experimental results are compared with time-dependent heat flow calculations based on the two-temperature model and the effect of number and separation time of two consecutive laser pulses with the same total fluence is studied for the Cr target. Moreover, the role of pulse width and absorbed fluence in thermal equilibrium time between electrons and lattice is investigated in two-temperature model. The thermal equilibrium between electron and lattice is established after a few picoseconds for low fluences and after a few tens of picoseconds at higher fluences.