Spurious-Free SAW Filters With Inherent Suppression of Transverse Modes on LiTaO3/SiO2/Quartz Platform

Piezoelectric heterostructures with piezoelectric single crystal bonded to handling substrate have emerged as a notable material platform for radio frequency filtering applications. However, spurious transverse modes resulting from the waveguide effect in the corresponding surface acoustic wave filters curtail the advancement of heterostructures in 5G data transmission. In this work, the
$\text{LiTaO}_{3}/\text{SiO}_{2}/\text{Quartz}$
platform was established to demonstrate several spurious-free SAW resonators and filters. Guided by the finite element methods and slowness analysis, AT-Quartz was selected as the optimal substrate to demonstrate effective suppression of transverse and highest admittance ratio simultaneously. The impact of the structure parameters of heterostructure-based resonators on transverse modes was then established step by step. Resonators and filters with various electrode thickness and materials were fabricated on the
$\text{LiTaO}_{3}/\text{SiO}_{2}/\text{Quartz}$
platform and
$\text{LiTaO}_{3}/\text{SiO}_{2}/\text{Quartz}$
platform for a comparison, among which a typical filter built on AT-Quartz demonstrated a minimum insertion loss as small as 0.89 dB, clean in-band response and excellent out of band performance simultaneously. The prototype highlights the strong potential of the
$\text{LiTaO}_{3}/\text{SiO}_{2}/\text{Quartz}$
acoustic platform for high-quality data transmission.