Tabletop Shock Wave Enhancement through Additive Superposition and Shock Focusing

Efficient shock excitation using lasers remains a technical challenge, ranging from compact tabletop systems all the way to laser fusion efforts at national laboratories. Here, we report progress in developing a multi-shock focusing methodology.

Our strategy exploits two approaches to shock enhancement: multiple-excitation shock velocity matching and shock focusing. First, we describe a route to generate successive laser pulses that are temporally delayed by nanoseconds and spatially shifted by microns, realizing a tunable laser scanning speed of several µm/ns, which can be adjusted to accurately match either a surface or longitudinal acoustic wave speed. [1] This allows amplification of a propagating wave through superposition of the responses to successive excitation pulses.

Second, we shape a laser pulse into a circular “ring” pattern at the sample. A focusing pressure wave can be generated by an excitation laser ring, converging at its geometric center with a roughly 10-fold enhancement of the stress. [2] In our most recent work, we are developing a technique to combine both enhancement strategies. We will discuss our proof-of-principle experiments showing two focusing shocks generated by two concentric rings of excitation laser light under speed-matching conditions. Finally, we will preview a design that employs metasurfaces to generate multiple concentric laser rings, providing a pathway toward experimental realization of strong shock amplification and compression on a tabletop.

[1] “Additive laser excitation of multiple surface acoustic waves up to the nonlinear shock regime,” J. Deschamps, Y. Kai, J. Lem, I. Chaban, A. Lomonosov, A. Anane, S. E. Kooi, K. A. Nelson, and T. Pezeril, submitted. arXiv:2209.13897 (2022).

[2] “Direct visualization of laser-driven focusing shock waves,” T. Pezeril, G. Saini, D. Veysset, S. Kooi, R. Radovitzky, and K.A. Nelson, Phys. Rev. Lett. 106, 214503 (2011).