SURFACE ACOUSTIC-WAVES IN NONLINEAR ELASTIC MEDIA

Various effects of elastic and piezoelectric nonlinearity on the propa gation of surface acoustic waves are discussed and methods for their t heoretical analysis are described. These effects include the frequency shift of surface acoustic waves due to externally applied static stre sses and electric fields, and the propagation of nonlinear surface wav es with emphasis on the characteristic differences between nondispersi ve and dispersive systems. Both types can occur in electroelasticity. In a homogeneous halfspace with a planar surface, surface acoustic wav es are nondispersive and resonant harmonic generation occurs. Wave for m evolution of surface waves propagating over long distances and the p ossibilities of waves of permanent form and localization of shear wave s at the surface due to nonlinearity are discussed. In the presence of dispersion, for example in coated media, effects like self-focussing, self-modulation and envelope solitons familiar from wave guide optics occur and it is shown in detail, how these phenomena follow from the basic equations of electroelasticity. Finally, the coupling of surface acoustic waves to thermal and quantum fluctuations via nonlinearity i s considered and the attenuation of surface waves resulting from this coupling is discussed in different temperature regimes.