Experimental Studies of Quality Factor Deterioration in Shear-Horizontal-Type Surface Acoustic Wave Resonators Caused by Apodization of Interdigital Transducer

Abstract

We investigate how the apodization applied to interdigital transducers (IDTs) affects the quality factor Q at the antiresonance frequency of surface acoustic wave (SAW) resonators. First, we fabricated SAW resonators with different apodization patterns on a SiO 2 /Cu/0°YX-LiNbO 3 structure, and showed that the Q factor become worse when the apodization becomes steeper and the IDT aperture is narrower. Next, it was shown by optical measurement that the Q degradation is mainly due to the radiation of SH waves from the resonator. The radiation consists of energy leakage as bulk waves, diffraction, and scattering of incident SAWs, and their strength strongly depends on the steepness of the apodization pattern.