A1 Resonators in 128° Y-cut Lithium Niobate with Electromechanical Coupling of 46.4%
Ruochen Lu, Yansong Yang, Steffen Link, Songbin Gong
Abstract
In this work, we present first-order antisymmetric (A1) mode resonators in 128° Y-cut lithium niobate (LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) thin films with electromechanical coupling coefficients (k <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) as large as 46.4%, exceeding the state-of-the-art. The achievable k <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of A1 in LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> substrates of different orientations is first explored, showing X-axis direction in 128° Y-cut LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> among the optimal combinations. Subsequently, A1 resonators with spurious mode mitigation are designed and fabricated. In addition to the large k <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , 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.