Properties of Surface Displacement of Saw Generated by Laser Induced by Instantaneous Inverse Piezoeffect

Abstract

The highest efficiency of light conversion into surface acoustic wave (SAW) has been achieved by laser action on a photoconducting piezocrystal, with the simultaneous application of an external electric field[1]. A theoretical analysis[2] supports the opinion of reference [1] that SAW excitation was primarily carried out by the inverse piezoeffect in the nonstationary electric fields induced by spatial separation of optically generated charge carriers ( i.e. instantaneous inverse piezoeffect). Their estimations show that the magnitude of conversion efficiency of optical power into SAW signal voltage obtained here may be three to seven orders higher than that obtained previously by thermoelastic mechanism of optoacoustic transformation. Telenkov et. al., [3] investigated the generation of SAW in high resistance CdS crystals under the action of a third harmonic of the YAG: Nd3+ pulsed laser. Experimental results show that the SAW excitation is due to the inverse piezoeffect. A linear dependence of the acoustic signal amplitude with applied external electric field is found. However, nobody analyses and calculates the property of surface displacement, as well as discuss the relationship between the distributions of surface displacement and properties of materials in frequency and time domains. It is worth for practical application.