Tabletop Shock Wave Enhancement through Laser-Shock Speed Matching and Energy Focusing

Efficient shock excitation using high-power lasers remain a technical challenge, evidenced by the effort invested at national laboratories to optimize the shock compression scheme for light elements. Here, we present an overview of several tabletop shock enhancement techniques developed by our group in the past few years, and then report our latest progress in developing a multi-shock focusing methodology.

The essence of shock enhancement is to implement the physical principles of speed matching and energy focusing. First, we reveal a route to generate successive laser pulses delayed in the nanosecond range and spaced by microns, realizing a tunable laser scanning speed in several µm/ns, which can be manually adjusted to accurately match either the surface acoustic wave or longitudinal wave speed of a condensed matter sample within a fraction of µm/ns as resolution. This allows the amplification of the pressure waves through superposition.

Second, we shape a laser pulse into a laser ring or multiple rings on condensed matter samples. A 2D focusing pressure wave can be generated by a laser ring, converging at its geometric center. Utilizing the energy focusing principle, the shock strength increases during the propagation and pivots at the focus, realizing 10 folds enhancement. The kernel of our most recent work is to develop a technique to implement both enhancement principles. We will discuss our proof-of-principle experiments showing two focusing shocks under speed-matching conditions. Subsequently, we will demonstrate a preview of our newly designed optical cavities combined with metasurfaces to generate laser rings, providing a pathway towards experimental realization of strong shock compression on a tabletop.