Abstract
Ablative formation of channels in steel by picosecond and nanosecond pulses of Nd lasers was studied. It was found that significant screening of the incident energy (up to 80–90%) in this pulse duration range is caused by breakdown of air contaminated with ablated microparticles. The breakdown threshold, size of particles, and time of their settling down were estimated. It was shown that this kind of plasma screening results in a decrease in the ablation rate and significant channel widening. Practical approaches to eliminate the low-threshold breakdown induced by microparticles were proposed and implemented. These approaches are based on experimental results of the study of the dependences of laser ablation on the pressure and repetition rate. It was shown that a moderate decrease in the pressure below 300–400 mbar makes it possible to avoid screening. In high-repetition-rate ablation, it was found that values above several kilohertz correspond to quasi-vacuum conditions in the ablation spot.
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Klimentov, S.M., Garnov, S.V., Konov, V.I. et al. Effect of low-threshold air breakdown on material ablation by short laser pulses. Phys. Wave Phen. 15, 1–11 (2007). https://doi.org/10.3103/S1541308X07010013
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DOI: https://doi.org/10.3103/S1541308X07010013