Pulsed nonlinear surface acoustic waves in crystals

Abstract

A theoretical model developed recently for the propagation of nonlinear surface acoustic waves in crystals [Hamilton et al., Nonlinear Acoustics in Perspective, edited by R. J. Wei (Nanjing U.P., Nanjing, 1996), pp. 64–69] is used to investigate transient effects associated with pulses. The present work extends an earlier theoretical investigation of pulsed nonlinear Rayleigh waves in isotropic solids [Knight et al., J. Acoust. Soc. Am. 96, 3322(A) (1994)]. The latter was verified via comparison with measurements of laser-generated nonlinear Rayleigh waves with shocks in fused quartz [Lomonosov et al., J. Acoust. Soc. Am. 101, 3080(A) (1997)]. Here simulations of waveform distortion and shock formation are presented for pulses in real crystals, including Si, KCl, and Ni, and for a variety of surface cuts and propagation directions. The second- and third-order elastic moduli in the nonlinearity matrix are taken from measurements reported in the literature. Attention is focused on waveforms corresponding to recent measurements of laser-generated nonlinear surface waves propagating in Si along the 〈112〉 direction in the (111) plane [Lomonosov and Hess, Nonlinear Acoustics in Perspective (Nanjing U.P., Nanjing, 1996), pp. 106–111]. Preliminary comparisons of theory with measurements obtained in related experiments are in good agreement. [Work supported by ONR and the RFBR Foundation.]