On photoacoustic monitoring of laser evaporation front movement

By the example of absorbing liquids (water, ethanol) irradiated by erbium laser pulses (λ = 2.94 μm), the possibility was experimentally demonstrated for detecting the displacement of the laser evaporation front by the phase shift (delay) of the acoustic response to a high-frequency (ω > 0.1 GHz) modulation of a laser pulse with the duration τ > 1/ω.