Linear and nonlinear elastic surface waves: From seismic waves to materials science

Surface acoustic waves (SAWs) were studied using pulsed laser radiation for excitation acid a cw laser for time-resolved detection of the propagating surface pulses. The dispersion of the phase velocity, caused by the inhomog eneous structure and morphology in CVD diamond plates, was used to obtain i nformation about the characteristics of this hard polycrystalline material. Strongly nonlinear SAWs were excited in silicon to study the anisotropic f eatures of elastic nonlinearity. The fracture of silicon by such nonlinear pulses could also be observed The propagation of solitary waves on a disper sive silicon plate, covered with a thin oxide film, was investigated. Fiber optic devices were employed to extend the frequency range of laser-generat ed SAW pulses into the gigahertz region.