Lithium Niobate Thin Film Based A3 Mode Resonators with High Effective Coupling Coefficient of 6.72%
Yi Zhang, Liang Wang, Yang Zou, Qinwen Xu, Jieyu Liu, Qing Wang, Alexander Tovstopyat, Wenjuan Liu, Chengliang Sun, Hongyu Yu
Abstract
In this paper, 600nm Z-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 film based third-order antisymmetric (A3) mode resonators with different geometries has been investigated. Through a series of experiments, it has been found for the first time that effective electromechanical coupling coefficient (K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) is influenced by the gap between electrodes (Ge), and K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> decreases with the increase of Ge when electrode pitch (P) higher than 5μm. Finally, a A3 mode resonator with a high 2 Keff of 6.72% is obtained. This K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is the highest reported value in similar acoustic resonators working about 9 GHz and will be beneficial to the construction of X-band filters.