Spatio-temporal behavior of laser induced plasma shock wave probed by optical beam deflection technique

Spatio-temporal evolution of Nd:YAG laser induced shock wave generated from copper target under various pump laser power densities (0.8-2.38 GW/cm2) at atmospheric pressure is investigated. Using optical beam deflection method, a supersonic shock wave is detected, it propagates in air and progressively decays into an acoustic wave. The results show that neither the point explosion blast wave model nor the drag force model is able to estimate the temporal evolution of the shock front. A power model considering the background pressure effect was suitable to fit the experimental data. The temporal behavior of the shock waves at different laser power densities is quite similar, but at higher laser power densities, a noticeable presence of reflected shock waves is seen. The effect of laser power density on the shock wave velocity is clearer near the target surface. A cooling wave with estimated velocity of 30 m/s is also detected.