Photoacoustic and evaporation pressure signals in water irradiated with erbium laser pulses

Pressure signals in water exposed to erbium laser pulses with a duration of 200 ns, a wavelength of 2.94 μm, and an intensity modulated with a period of ∼ 5 ns due to mode beats were studied. It was found that the amplitude of the high-frequency component of the pressure signal, caused by this modulation, reproduces the behavior of the smooth component of the laser pulse shape at low irradiation intensities. As the intensity increases, behavior of the high-frequency signal amplitude is more complicated, showing significant decrease at certain instants of laser pulse exposures. Such behavior can be caused by the simultaneous effect of photoacoustic and evaporation mechanisms of pressure generation in irradiated liquid.