Abstract
In this work, the relation between temperature coefficient of frequency (TCF) and wavelength () of a shear horizontal surface acoustic wave (SH-SAW) resonator in lithium niobate-on-insulator (LNOI) platform is investigated numerically and experimentally. Proposed device achieves a low TCF of -18.5 ppm/K, quality factor (Qmax) of 1360, and effective electromechanical coupling factor ({k_{{eff}}}2}) of 21.2%, yielding a high figure-of-merit ({{FOM1}} = k_{{eff }}}2{Q_max }}}) of 288. The dispersive behavior of the TCF was first analyzed based on finite element method (FEM), which reveals the strong correlation between TCF and the thickness of LN (hLN) and SiO2 (hSiO2) thin films. To confirm our observations, three prototyped SH-SAW devices with of 2.8, 4, and 6m were fabricated and characterized, showing TCFs approximately -86, -45, and -18.5 ppm/K, respectively, for both series and parallel resonance frequencies. The results captured through experiments fits well with the trends predicted in the FEM simulations. Furthermore, the proposed resonator (6m, TCF = -18.5ppm/K, FOM1 = 288) exhibits a very competitive performance among state-of-the-art thin film LN/LT resonators.