Measurement of Velocity of Surface Acoustic Waves on Proton-Exchanged Lithium Tantalate Using Comb Filters

Abstract

The phase and group velocities of surface waves on z-cut proton-exchanged lithium tantalate were measured. Lithium ions were exchanged for hydrogen ions in heated pyrophosphoric acid. The insertion loss of the filters, which were formed directly on the exchanged layers, was nearly equal to the loss on unexchanged lithium tantalate. The reduction of the phase velocity was proportional to the thickness of the exchanged layers. The reduction was 3.8% for x-propagating surface waves when the layer thickness normalized by the surface wavelength was 0.082. The reduction of the group velocity was 6.4%, which was nearly equal to the reported value of z-cut lithium niobate.