Q-enhanced Lithium Niobate SH0 Resonators with Optimized Acoustic Boundaries

In this work, a quality factor (Q) enhancement technique has been investigated for the fundamental shear-horizontal (SH0) mode lithium niobate resonators. Four supporting tether designs are employed in combination with an optimized release distance to enhance the acoustic isolation and consequently attain a higher Q without introducing spurious modes. The fabricated prototype resonator with tapered tether design at 90 MHz exhibits a Q of 2,600 and an electromechanical coupling (k
_t
²
) of 17%, resulting in a high figure-of-merit (FoM= k
_t
²
×Q) of 442. The Q of 2,600 underlines a 2X Q enhancement from a conventional straight supporting design. The perfectly matched layer (PML) method is adopted to optimize the energy loss with different acoustic boundaries. Results from our comprehensive finite-element analyses (FEA) are also reported to rationalize our design choices and confirm a Q estimation error within 15% of the measured values.