Double-layer LiNbO3 longitudinally excited shear wave resonators with ultra-large electromechanical coupling coefficient and spurious-free performance

This work proposes a double-layer lithium niobate (LiNbO3) longitudinally excited shear wave resonator with an ultra-large electromechanical coupling coefficient(keff2). When the rotation of the two films is different by a certain angle, the resonator will obtain the keff2 exceeding 55%, RaR close to 26%, and no spurious mode. This ultra-large keff2 is much larger than all LiNbO3 acoustic resonators reported so far. The resonator design is flexible, because the main performance can be monotonically adjusted with the change of structural parameters. With the development of the new generation of piezoelectric resonators, this ideal and streamlined resonator is expected to become a key solution for, e.g., high-performance acoustic filters, power converters, and mechanical antennas, working from very low frequency to super high frequency.