Generation of shock waves by laser-induced plasma in confined geometry

TLDR

The study employs a 1.06 µm neodymium glass laser with 3‑ and 30‑ns pulses to generate confined plasmas on a metallic target coated with a dielectric layer, noting that the breakdown threshold depends on pulse rise time. Pressure measurements agree with an analytical model at moderate power densities, but at 10 GW cm⁻² dielectric breakdown limits pressure, saturating it; employing short‑rise‑time pulses mitigates breakdown and produces much higher shock‑wave pressures.

Abstract

Confined plasmas induced by neodynium glass laser at 1.06 μm and pulse width of 3 and 30 ns are studied. The metallic target is covered with a dielectric layer, glass or water, transparent to the laser radiation. Experimental measurements of the pressure induced by the plasma have been performed. For a certain range of laser power density these measurements agree particularly well with an analytical model. At high power densities (10 GW/cm2), the dielectric breakdown appears to be the main limiting process of the confining method. It is observed that this breakdown induces a saturation of the pressure. It is shown that the use of a short-rise-time laser pulse is the only way to reduce the effects of the breakdown and to obtain much higher-pressure shock waves. This is due to the dependence of the dielectric breakdown threshold on the laser pulse rise time.