Publication
Applied Physics Letters
Paper

On the precursor in laser-generated ultrasound waveforms in metals

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Abstract

A laser pulse, when focused on a metal sample, produces characteristic elastic waveforms, which depend on whether thermoelastic or ablative/evaporative mechanisms dominate the generation process. In the thermoelastic regime, with an unconstrained surface, the predominant axial displacement is opposite to the direction of propagation (negative), but there is typically a small transient positive displacement. This precursor is not predicted by elastic point source models, but is predicted by models including thermal diffusion. A recent formulation of pulsed photoacoustic generation is used to show how the precursor arises from interaction of the thermal and elastic modes at the illuminated surface.

Date

01 Dec 1990

Publication

Applied Physics Letters

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