Profile of laser-produced acoustic pulse in a liquid

Recently, Lai and Young [J. Acoust. Soc. Am. 72, 2000 (1982)] and Heritier [Opt. Commun. 44, 267 (1983)] have independently calculated the profile of a thermo-elastically generated optoacoustic pulse due to the passage of an excitation laser pulse of certain spatial and temporal intensity distributions in a weakly absorbing medium. We have found that their results are essentially equivalent for Gaussian intensity distribution of the excitation laser. We report the first experimental verification of such theoretical opto-acoustic profiles excited by laser pulses of various pulse widths TFWHM„ (8 ns and 1.3//s) focused to different beam waists w0. Our observation of the profile is performed with a probe beam deflection technique instead of using conventional acoustic transducers which have limited rise times and nonflat frequency response. Our results are in reasonable agreement with theory, and clearly indicate that sharp opto-acoustic pulses can be generated by laser pulses of short rFWHMand small w0. © 1984, Acoustical Society of America. All rights reserved.