Anomalous dispersion of SAW in platinum grating on langasite with Euler angles (0°, 138.5°, 26.6°)

Abstract

The numerical technique recently developed for simulation of SAW dispersion in periodic gratings was applied to langasite cut with Euler angles (0°,138.5°,26.6°) and platinum grating, when electrode thickness varies between 1% and 6% λ (SAW wavelength). Analysis has revealed that with increasing Pt thickness, the dispersion appears to be strongly affected by interaction between two SAW modes. It results in additional stopband, which occurs at certain detuning from synchronous reflection condition and manifests itself by additional resonances of admittance function if such detuning occurs in SAW resonator. The anomalous character of dispersion is not adequately described by the known COM models and can explain the slow growth of reflectivity with increasing electrode thickness.