Phase-change phenomena and acoustic transient generation in the pulsed laser induced ablation of absorbing liquids

The mechanisms of the pulsed laser-induced ablation of strongly absorbing liquids and generation of acoustic transients are studied in the present work. Aqueous solutions of K2CrO4 and pure water are irradiated by a KrF excimer laser (lambda = 248 nm, FWHM = 24 ns) and a CO2 laser (lambda = 10.6 mu m, variable pulse duration), respectively. The ablation process, including the vapor cavity formation and the acoustic wave propagation, is visualized by laser flash photography. The measurement of acoustic transients is performed by a piezoelectric pressure transducer. Simultaneous detection of acoustic wave and optical transmission is also carried out to reveal the vapor-phase dynamics. The mechanisms of liquid ablation and acoustic pulse generation are examined on the basis of the thermoelastic behavior of the liquid medium and the evaporation dynamics. (C) 1998 Elsevier Science B.V.