Shear horizontal mode surface acoustic wave resonator with ultra-high electromechanical coupling based on the X-cut LNOI acoustic platform

Shear horizontal surface acoustic wave resonators (SH-SAWRs) based on lithium niobate thin films on insulator (LNOI) platforms exhibit high electromechanical coupling and hold significant potential for applications in devices operating at frequencies exceeding gigahertz (GHz). This work presents the SH-SAWR with a resonance frequency of 2 GHz and high effective electromechanical coupling coefficient (keff2) of up to 42%. Finite element analysis (FEA) and theoretical studies were combined to optimize the structural parameters of the device for higher keff2 and larger quality (Q) factor, with the measured results effectively validating the proposed designs. Compared to devices without grating reflectors (GRs), the Q factor can be increased by over twofold with floating GRs and by threefold with grounded GRs. Our results show the outstanding performance of SAW resonators based on LNOI, promising for ultrawideband wireless communications.