Picosecond double-pulse ablation in silicon and aluminium with variable delay

Double-pulse ablation with picosecond pulses is a promising way to maximize the efficiency of the ablation due to plasma and thermal effects. Therefore, the increase of material ablation rates in Silicon and Aluminium using picosecond double-pulses instead of single pulses is examined. The experiments are performed with pulse durations of 8.5 ps and a wavelength of 1064 nm. The double-pulses are generated using a Mach-Zehnder interferometer setup to be flexible in choosing the delay between the two pulses from a few picoseconds up to several nanoseconds. We show that the progress of ablation rate per pulse is highly influenced by the inter pulse separation and reaches global maxima depending on material properties. Furthermore we present first results of the investigations of ablation shape and surface roughness.