Electroacoustic interaction between SAW and vibration modes of high-aspect-ratio electrodes built using LIGA-UV techniques on singly rotated lithium niobate wafers

It has been shown theoretically and demonstrated experimentally that shear horizontal surface waves can exist when the surface of an isotropic substrate is perturbed by a strong corrugation, for instance consisting of deep grooves etched in the substrate, whereas these waves cannot exist without this perturbation. In this work, we analyze the behavior of surface acoustic waves with general polarization propagating under a periodic array of metallic electrodes with large aspect ratio, deposited over a piezoelectric substrate. In this case, we had previously predicted the existence of generally polarized higher order surface modes. We have constructed high-aspect-ratio interdigital transducers (IDTs) on Y+128 lithium niobate using electroplating techniques. We have observed the existence of higher order surface modes using electrical measurements of the admittance of the IDTs. The predicted and experimental results agree reasonably well, although more work is required to fully understand the properties of these higher order surface modes of high-aspect-ratio IDTs.