The effect of intra-pulse number during burst mode picosecond laser ablation of 316 stainless steel: Experimental and numerical modelling

An experimental and numerical analysis of 10 ps laser ablation on 316 L stainless steel at 100 KHz with 30 MHz intra-burst frequency and varying intra-burst number is reported. This research experimentally revealed how intra-pulse number N_int (1–5) influences the ablation threshold and ablation depth while a Two-Temperature Model (TTM) coupled with material removal method is used to predict the transverse temperature and ablation profile during pulse burst ablation. It was found that the intra-pulse ablation threshold F_int decreases and ablated depth D_exp increases with increasing N_int. The numerical results align well with the experimental data, assuming that the heat accumulation is the main mechanism. However, melting and thermal stress is more pronounced when N_int > 3 resulting in the highest annular bulge at N_int = 5. The results not only highlight the importance of intra-pulse number on the ablation efficiency, but also provide an insight into the physics of MHz burst mode in picosecond laser ablation.