Surface acoustic wave resonator using layered phononic crystals

Phononic crystals (PnC) perform band gaps and promise applications such as filters and reflectors. Traditional PnC for surface acoustic waves (SAW) consisting of deep periodic holes in half space. To apply PnCs in SAW devices, the feasibility of fabrication was considered and layered PnCs were proposed. In this paper, a PnC comprised of cylindrical holes in a SiO₂ layer covering a 128°rotated Y-cut LiNbO₃ substrate was analyzed numerically and used to design SAW resonators. Acoustic dispersion of SAWs in the PnC was calculated by finite element method and the band gap range was indicated. The band gaps were manipulated by the layer thickness and cylinder size. Then the layered PnC was applied as gratings to reflect SAWs. Resonant cavities for SAW were further designed, and a 942.875 MHz SAW resonator with Q-factor of 433 was obtained. The result showed feasibility of applying PnC in acoustic electronics devices via MEMS fabrication.