The elastic-plastic response of aluminum films to ultrafast laser-generated shocks

TLDR

The study investigates the free surface response of 2, 5, and 8 µm aluminum films to shocks generated by chirped ultrafast lasers. Shocks are produced by chirped ultrafast lasers and the resulting free surface velocities are measured to characterize the elastic and plastic wave propagation. The data show two distinct elastic and plastic wave steps, with elastic velocities up to 1.4 km/s (12 GPa), rapid decay with increasing film thickness, and a strong dependence of wave magnitudes and temporal separation on laser drive energy, resolving the separation to as short as 20 ps.

Abstract

We present the free surface response of 2, 5, and 8 μm aluminum films to shocks generated from chirped ultrafast lasers. We find two distinct steps to the measured free surface velocity that indicate a separation of the faster elastic wave from the slower plastic wave. We resolve the separation of the two waves to times as short as 20 ps. We measured peak elastic free surface velocities as high as 1.4 km/s corresponding to elastic stresses of 12 GPa. The elastic waves rapidly decay with increasing sample thickness. The magnitude of both the elastic wave and the plastic wave and the temporal separation between them was strongly dependent on the incident laser drive energy.