A1 Resonators in 128° Y-cut Lithium Niobate with Electromechanical Coupling of 46.4%

Abstract

In this work, we present first-order antisymmetric (A1) mode resonators in 128° Y-cut lithium niobate (LiNbO₃) thin films with electromechanical coupling coefficients (k²) as large as 46.4%, exceeding the state-of-the-art. The achievable k² of A1 in LiNbO₃ substrates of different orientations is first explored, showing X-axis direction in 128° Y-cut LiNbO₃ among the optimal combinations. Subsequently, A1 resonators with spurious mode mitigation are designed and fabricated. In addition to the large k², the implemented devices show a maximum quality factor (Q) of 598 at 3.2 GHz. Upon further optimization, the reported platform can potentially deliver a wideband acoustic-only filtering solution in 5G New Radio. [2020-0003]