Ultrasonic generation by pulsed UV lasers
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In this paper, a Q-switched, frequency doubled ruby laser has been used to generate ultrasonic transients in both metals and water, at a wavelength of 347 nm in the UV.Abstract:
A Q‐switched, frequency doubled ruby laser has been used to generate ultrasonic transients in both metals and water. The laser source delivered multimode pulses, of 30‐ns duration and energy ⩽200 mJ, at a wavelength of 347 nm in the UV. Displacements generated in metal plates were detected by wideband capacitance transducers, and compared to wave propagation theory. Thermoelastic, ablative, and modified surface sources were examined, and a good correlation between experiment and theory obtained. In addition, wideband directivity patterns in aluminum were obtained for the thermoelastic source. Thermal generation in water with a cylindrical geometry was also examined, and the expected dipolar pressure transients recorded. It was shown that their duration was a function of the multimode laser beam diameter over the 1.5‐ to 4‐mm range.read more
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