Resonant properties of fast leaky surface acoustic waves on lithium niobate

Fast leaky surface acoustic waves in lithium niobate correspond to complex valued singular points of effective permittivity function. Due to the trapping effect under large periodical loading these waves effectively resonate in long IDTs. The admittance characteristics of an infinitely long IDT are analyzed in the complex plane of frequencies. The poles and zeros of the admittance represent the resonant and anti resonant frequencies respectively. The position of poles and zeros as a function of electrode height to wavelength ratio has been calculated. It is shown that in IDTs with thick aluminum electrodes together with the Rayleigh wave resonance a new additional resonance occurs in the low frequency region where there is no energy dissipation into the bulk waves. This new resonant behavior can be associated with an interaction between the Rayleigh wave and a leaky wave with high intrinsic attenuation