Pressure generation and measurement in the rapid vaporization of water on a pulsed-laser-heated surface

Abstract

The transient pressure generated by the interaction of short-pulsed laser light with the liquid–solid interface is studied quantitatively. A KrF excimer laser beam of tens of nanoseconds pulse duration irradiates water on a solid surface and induces rapid thermal expansion and explosive vaporization. The pressure pulses launched into water by such processes are detected experimentally by the photoacoustic probe beam deflection method and a broadband piezoelectric transducer. The peak intensities of the traveling pressure wave measured by these two methods are compared with the theoretical thermoelastic predictions. The measurements show that a compressional pressure wave packet is radiated from the water-solid interface with the peak intensity of the order of 1 MPa at laser fluences up to about 100 mJ/cm2. Simultaneous monitoring of the bubble growth kinetics by the optical specular reflectance probe has been performed. It is observed that the pressure generation is enhanced by the bubble expansion in the superheated water for laser fluences exceeding the bubble nucleation thresholds.