S₀ mode lamb wave resonators using LiNbO₃ thin plate on acoustic multilayer reflector

Lamb wave modes can be classified as a fundamental anti-symmetric mode (A0), a symmetric mode (S₀), and their higher order modes. Membrane-type A1 mode Lamb wave resonators have been reported by the authors for future mobile communication systems. Although the reports show promising results, it is difficult to fabricate the resonators because they have a large dispersion of phase velocity and electromechanical coupling factor, and also are fragile. In this study, the authors suggest a solidly mounted resonator (SMR)-type S₀ mode Lamb wave resonator, which can solve the above-mentioned difficulty. An SMR-type S₀ mode Lamb wave resonator was successfully realized for the first time. The resonator exhibits a 1.5 times faster phase velocity and a 1/3 smaller temperature coefficient of frequency than the commonly used surface acoustic wave (SAW) devices composed of an Al electrode and a 36-48YX-LiTaO3 substrate.