Effect of piezoelectricity on the excitation and radiation of acoustic waves in rotated Y-cut quartz

Abstract

Recently we reported a far field theory of transverse acoustic waves radiated from an interdigital transducer deposited on a singly rotated quartz crystal. This was done by an approximation called the local decoupling approach, allowing us to consider electrical effects as forcing fields for the mechanical motion. The present analysis demonstrates that this approximation is not valid in predicting the complete spectrum of acoustic waves. It is shown that near the cutoff frequency the bulk wave may be converted into a surface wave of Bleustein–Gulyaev type in the free surface case, and that a surface metallization reinforces the strength of this conversion. Velocity of surface waves are determined by means of the effective permittivity function and correct radiation diagrams are plotted in the far field.