MODE CONVERSION COEFFICIENTS OF ACOUSTIC WAVES AT A CRYSTAL-VACUUM INTERFACE

Abstract
Recent work by Taborek¹ et al has shown that the reflection of acoustic phonons from a sapphire-vacuum interface is divided between a specular component which is predicted by elastic theory and a diffuse component. Knowledge of the magnitude and direction of the specular component is useful in the design of experiments to study the frequency dependence of the reflection process. We have generated mode conversion coefficients for infinite plane waves traveling initially in the x direction and incident at various angles on perfect surfaces in quartz, sapphire, and ZnO. For waves propagating in the xy-plane, ZnO behaves as an isotropic solid whereas quartz, because of its anisotropy, exhibits new transverse reflections beyond the critical angle.