Fundamental investigations of ps-laser burst-mode on common metals for an enhanced ablation process

摘要

In this study, ps-laser micromachining of different types of metals like copper, aluminum, titanium, tungsten and zinc have been investigated. Their single-pulse damage thresholds for the laser wavelengths of 355 nm, 532 ran and 1064 nm were experimentally determined. The laser-induced surface morphology both in the low and high fluence regime, as well as in the transition area, were examined for all investigated metals by scanning electron microscopy. Single pulse experiments and multi-pulse ablation experiments for up to 6 pulses using time-delays between successive pulses of 1 s and 20 ns were carried out. Our observations show that the surface morphologies significantly change from single-pulse ablation to the application of a second pulse. By comparing different separation times in the multi-pulse experiments we show that the burst-mode in ps-laser processing accumulates heat. This results in strong arising melting films, smoothing of the ablation craters and melt splashes outside of the crater. We found out, that copper and aluminum as well as titanium and zinc show similar ablation behavior by using the burst mode.