Optimization of aperture in SAW and STW resonators on langasite

A numerical technique developed for simulation of admittance of a finite-aperture resonator is applied to three LGS orientations: YX-cut, SAW cut with Euler angles (0°, 138.5°, 26.7°) and STW cut, Euler angles (0°, 22°, 90°), with a periodic platinum grating. The degradation of a resonator performance is observed for each cut when a resonator aperture decreases from 100 to 20 wavelengths. The ripples of the admittance function are analyzed in correlation with the slowness surface varying with the electrode thickness. Some specific features of each analyzed orientation, such as strong anisotropy or interaction with parasitic modes, and their impact on the resonator performance are discussed. The minimum acceptable aperture is determined for each cut and the possibility of decreasing it without further degradation of admittance, by variation of electrode thickness, is analyzed.