In Situ Analysis of Ultrashort Pulse Burst Ablation via Transmission Pump Probe Imaging

Within the research topic of the application of high-power ultrashort pulsed (USP) laser beam sources to increase the productivity of USP processes different approaches are being pursued. Pulse bursts enable the utilization of higher average powers but shielding effects and heat accumulation are amplified by the small temporal and spatial distances between consecutive pulses. Additionally, the investigations on bursts have uncovered a new behavior for aluminum and copper, which is not fully understood yet. The article evaluates ex situ and in situ experiments for copper ablation with one to four pulses per burst. The varying ablation behavior between even and uneven numbers of pulses per burst are investigated and the changes in the ablation dynamics are described. The parameter variation for the ex situ experiments shows a dependency of the alternating efficiency effect on the applied pulse energy. Furthermore, the occurrence of this effect is demonstrated for single burst ablation on copper. Based on the comparison of the ex situ and in situ data obtained by pump probe transmission microscopy, the changing ablation dynamics for the different burst types are described qualitatively.