Effect of surface-bulk hybrid mode on strip admittance in 42°YX and 48°YX cuts of LiTaO3 with Al grating

We report on a study of the effect produced by the surface-bulk hybrid (SBH) mode on the performance of resonators built on 42°YX and 48°YX cuts of LiTaO₃(LT). An approximation was suggested for SBH mode effect on harmonic admittance, and the main parameters of this mode were extracted from numerically found admittance, as functions of electrode thickness, metalization ratio and detuning factor. In both orientations, effective electromechanical coupling of SBH mode reduces with electrode thickness and increases with metalization ratio. Maximum coupling occurs when the detuning from synchronous resonance is about (0.4-0.6)%. In 48°YX-LT, SBH mode is much stronger attenuated than in 42°YX-LT and its effect on strip admittance is less apparent. The simulated behavior of SBH mode shows good agreement with experimental data.