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ISSN Online: 2377-424X

ISBN Print: 1-56032-797-9

International Heat Transfer Conference 11
August, 23-28, 1998, Kyongju, Korea

Ablation Threshold and Pressure-Pulse Generation In the Pulsed-Laser Irradiation of Absorbing-Liquid Surface

Get access (open in a dialog) DOI: 10.1615/IHTC11.220
pages 129-134

Аннотация

The pulsed-laser-induced ablation of strongly absorbing liquids and the generation of acoustic transients for laser fluences around the ablation threshold are studied in the present work. Aqueous solutions of K2CrO4 and pure water are irradiated by a KrF excimer laser (λ=248 nm, FWHM=24 ns) and a C02 laser (λ=10.6 µm, variable pulse duration), respectively. The acoustic-transients and vapor-cavity dynamics are measured by a piezoelectric-pressure transducer and an optical-transmission probe, respectively. The dynamics of surface deformation and vapor-cavity formation by C02-laser irradiation of water surface is visualized by laser-flash photography. The experiments show that the excimer-laser ablation of K2CrO4 solutions is initiated by the tensile component of the produced thermoelastic stress. In contrast, the ablation of water by C02 laser is governed by thermal evaporation without significant acoustic-field effect. It is also found that growth of the surface cavity formed by C02 laser irradiation is inhibited by hydrodynamic instability. In addition, the collapse of the cavity releases a cavitation-pressure pulse in the water. The physical mechanisms of the instability are discussed on the basis of hydrodynamic-stability theory.