Pulse width dependent dynamics of laser-induced plasma from a Ni thin film

Abstract

Plasma plume formation and its expansion in the background gas are investigated in a 50 nm thick Ni thin film under the rear ablation/laser blow-off (LBO) geometry, employing 10 ns, 200 ps and 100 fs laser pulses respectively. Plume directionality, splitting and expansion are found to depend on the laser pulse width, and the expansion behavior is explained by appropriate models. In the case of fs ablation, the plume shows a linear expansion at lower background pressures, while at higher pressures the expansion appears to show shock wave like nature. For ps ablation the expansion appears to follow a blast wave model at lower pressures, which, however, fits with drag model at higher pressures. In case of ns ablation, shock wave like nature is observed for all the pressures. Further, we believe the present study may have potential implications in pulsed laser deposition, ultra fast laser based nano particle generation and micro-machining.