Nanostructures’ difference for differing band gap materials during ultrashort double-pulse laser ablation

Abstract

The ultrashort double-pulse ablation of fused-silica glass, silicon, and stainless alloy is investigated. The time delay between the two pulses ranges from 0 fs to 3 ps. It is revealed that when the ablation rate is limited, the laser-induced periodic surface structures become very shallow and some nanodroplets are attached to them during the double-pulse ablation. In addition, from energy-dispersive X-ray spectroscopy analysis, the oxygen atoms are observed to be not effectively consumed and remain in the shallow nanostructures. On the basis of this, the craters created by the double-pulse laser with different time delays are studied in detail. The results indicate that the method can increase the ablation depth of these materials with certain exceptions. For fused-silica glass, as the time delay increases, the ablation depth first increases and then decreases, while for silicon and stainless alloy, the ablation depth first increases with time delay and then starts to drop after reaching the maximum value. Afterwards it increases again.