Phononic band gaps in periodically corrugated lithium niobate plate.

Abstract

A ZX-cut lithium niobate crystalline plate with a periodic corrugation is shown to have the band gaps in its spectrum of the plate acoustic waves. The corrugated plate is modeled numerically using finite element method. The depth of corrugations is 20% of the plate thickness along the Z-axis, and the corrugation period along the X-axis is taken from 0.3 to 1 mm for different model samples. The phase and group velocities of propagating acoustic modes will be affected significantly by the periodic change of plate thickness. The cutoff frequencies of higher-order modes will increase, and some new plate acoustic waves will appear. The periodic corrugations will cause the reflections and band gaps in the spectra of propagating modes. The strongest effects occur when the period of corrugations is equal to an integer number of half wavelengths of a mode. However, the distortions of the spectra do not appear in the spectrum if only 10% of the plate length is corrugated. One can achieve a complete band gap with certain corrugation periods and plate thicknesses. A periodically poled corrugated LiNbO3 is also considered. These acoustic properties of a phononic LiNbO3 crystal may be employed in a new generation of acoustic filters.