Generally polarized acoustic waves trapped by high aspect ratio electrode gratings at the surface of a piezoelectric material

It has been shown theoretically and demonstrated experimentally that shear horizontal (SH) surface waves can exist when the surface of an isotropic su bstrate is perturbed by a strong corrugation, for instance consisting of de ep grooves etched in the substrate, whereas these waves cannot exist withou t this perturbation. It is shown in this article that a periodic array of m etallic electrodes (wires) exhibiting large aspect ratios deposited over a piezoelectric substrate give rise to surface acoustic waves with general po larization. The admittance of an interdigitated transducer, which is a basi c tool for predicting the waves parameters, is calculated by a combination of finite element analysis and a boundary integral method. This approach ha s been extended to obtain the polarization of the acoustic waves. For diffe rent piezoelectric substrates, we predict various surface acoustic modes an d their polarization. Along with mostly SH modes, we also find modes mostly polarized in the sagittal plane. We discuss the frequency behavior of the surface modes as a function of the electrode height compared to the period. (C) 2001 American Institute of Physics.