We report an ablation enhancement (both deepening and widening in ablation profiles) on nickel by ultrashort double-pulse laser irradiation, an exception of the typical reduction trend observed in ablation rates for metals irradiated with double-pulse excitations. Maximized at a pulse-separation (τs) of approximately 4 ps, the enhancement was observed before τs was increased to approximately the electron-lattice energy relaxation time. An achievement of ablation, by temporal shaping a weak pulse with energy well below the single-pulse ablation threshold into two considerably weaker pulses, was demonstrated. It is proposed that the enhanced electron-phonon coupling and drop of electronic heat conductivity, both of which result from the reductions in electron temperature (by pulse shaping), co-contribute to the widening in ablation profiles, while the former one is responsible for the deepening. This letter proposed an ablation enhancement approach to ultrashort laser processing of nickel.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)