Non-radiative complete surface acoustic wave bandgap for finite-depth holey phononic crystal in lithium niobate

We demonstrate the existence of non-radiative complete surface acoustic wave (SAW) bandgaps for two-dimensional piezoelectric phononic crystals of holes. Holes of finite depth in a semi-infinite LiNbO 3 substrate are specifically considered. SAW bandgaps are determined from the band structure calculated with a three-dimensional finite element method taking into account material anisotropy and piezoelectricity. The effect of hole geometry on the bandgaps has been investigated. It is further found that the complete band gap does not close for moderately conical holes