Interferometric analysis of cylindrically focused laser-driven shock waves in a thin liquid layer

Abstract

We apply time-resolved interferometric imaging to study laser-driven focused shock waves on the microscale. Shock waves are generated in a 10 μm-thick layer of water by sub-nanosecond laser pulses focused into a ring of 100 μm radius. Imaging is performed with a Mach-Zehnder interferometer by time-delayed femtosecond pulses. We obtain a series of images tracing the converging shock wave as it collapses to a focal point and then reemerges as a divergent shock wave eventually leaving behind a cavitation bubble at the focus. Quantitative analysis of interferograms yields density and shock velocity values that match the water Hugoniot data found in the literature. In a separate development, we captured the propagation of cracks in a glass substrate initiated by focused shock waves. The results open the prospect of spatially resolved studies of shock-compressed materials in a small-scale all-optical experiment.