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

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.