In-Situ Analysis of Ultrashort Pulsed Laser Ablation with Pulse Bursts

Laser ablation using ultrashort pulsed (USP) laser sources enables contact free materials processing with very high precision at negligible thermal influence for the processed workpiece. However, the achieved productivity is still too low for industrial applications in many cases. To increase the throughput of USP laser processes, three approaches are followed: high repetition rates up to several MHz using fast beam deflection techniques, pulse bursts or parallel processing with multiple laser foci. In case of high repetition rates and pulse bursts the temporal and spatial distance of consecutive pulses becomes so small that heat accumulation and shielding effects of plasma and particles affect the processing quality and achieved efficiency significantly. In order to gain a better insight of these still barely investigated effects we apply in this work in situ imaging with an ICCD camera during ablation processes of copper and stainless steel with pulse bursts to evaluate the excitation of process luminescence as well as its relation to ablation efficiency and shielding effects.