On the precursor in laser‐generated ultrasound waveforms in metals

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