Profile of Laser-Produced Acoustic Pulse in a Liquid.
IBM RESEARCH LAB SAN JOSE CA
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Recently, Lai and Young have independently calculated the profile of a thermo-elastically generated opto-acoustic pulse due to the passage of an excitation laser pulse of certain spatial and temporal intensity distributions in a weakly absorbing medium. The authors of this document have found that Lais Youngs results are essentially equivalent for Gaussian intensity distribution of the excitation laser. The authors report the first experimental verification of such theoretical opto-acoustic profiles excited by laser pulses of various pulse widths tau FWHM 8 nsec and 1.3 microsecs focussed to different beam waists w sub o. Observation of the profile is performed with a probe beam deflection technique instead of using conventional acoustic transducers which have limited risetimes and nonflat frequency response. The authors are in reasonable agreement with theory, and clearly indicate that sharp opto-acoustic pulses can be generated by laser pulses of short tau FWHM and small w sub o.
- Lasers and Masers