A numerical investigation of HVPSAW in LiTaO3 with uniform gold film and periodic gold grating

The paper reports on the results of numerical investigation of high-velocity pseudo-surface waves (HVPSAW) in θ-rotated Y-cuts of lithium tantalate (LT), 90°-propagation. Attenuation coefficients of HVPSAW are compared for LT with Au uniform film and with Au periodic grating. The results are presented as contour plots of attenuation versus film or electrode thickness and rotation angle. HVPSAW degenerates into a pure HVSAW when θ=29° and 127°, with Au film thickness h/λ=4.8% and 5.0%, respectively. These optimal orientations move to θ=39° and θ=118°, in a substrate with Au grating, with optimal electrode thickness reduced to h/λ=2.55%. In both orientations low-attenuated HVPSAWs exhibit fairly high piezoelectric coupling (2-6%). Analysis of strip admittance confirmed that HVPSAW resonator with high quality factor can be built on the found orientations. Velocity dispersion curve was calculated for the optimal cut with the grating of optimized thickness