Generation of Shear Waves by Laser in Soft Media in the Ablative and Thermoelastic Regimes

TL;DR

This paper investigates laser-induced shear wave generation in soft media, identifying thermoelastic and ablative regimes, supported by experiments and modeling, with implications for laser-based elastography.

Contribution

It introduces a physical model for shear wave generation by laser in soft media, distinguishing two regimes and validating with experiments and simulations.

Findings

Shear waves are generated in soft media using laser beams.

Two regimes identified: thermoelastic and ablative.

Theoretical and experimental results are in close agreement.

Abstract

This article describes the generation of elastic shear waves in a soft medium using a laser beam. Our experiments show two different regimes depending on laser energy. Physical modeling of the underlying phenomena reveals a thermoelastic regime caused by a local dilatation resulting from temperature increase, and an ablative regime caused by a partial vaporization of the medium by the laser. Computed theoretical displacements are close to experimental measurements. A numerical study based on the physical modeling gives propagation patterns comparable to those generated experimentally. These results provide a physical basis for the feasibility of a shear wave elastography technique (a technique which measures a soft solid stiffness from shear wave propagation) by using a laser beam.