BULK AND SURFACE ACOUSTIC WAVES IN ANISOTROPIC SOLIDS

Abstract

In this paper methods for analyzing acoustic propagation characteristics for bulk and surface acoustic waves in anisotropic piezoelectric multilayers are described. The methods's conceptual usefulness is demonstrated by examples showing how problems of guided wave propagation in complicated layered surface acoustic wave device geometries are simplified. The formulation reduces the acoustoelectric equations to a first order ordinary matrix differential equation in the variables that must be continuous across interfaces. The solution to these equations is a transmission matrix that maps the variables from one layer face to the other. Interface boundary conditions for a planar multilayer are automatically satisfied by multiplying the individual transmission matrices in the appropriate order thus reducing the problem to imposing boundary conditions appropriate to the remaining free surface. The dimensionality of the problem being independent of the number of layers is a significant advantage. A classification scheme for reducing problem dimensionality, based on an understanding of crystal symmetry properties, further simplifies surface acoustic wave problems.