Propagation of Surface Acoustic Waves in two-dimensional periodic structures

Propagation of Surface Acoustic Waves (SAW) in two mutually perpendicular directions on the substrate of YZ-cut of LiNbO₃ with two-dimensional periodic surface corrugations has been investigated. To calculate the distribution of wave amplitudes as well as SAW transmission and reflection coefficients a new method based on 2D-transfer matrices was developed. Frequency dependencies of transmission and reflection coefficients for Rayleigh SAW propagating in a rectangular region occupied by the two-dimensional periodic structure with three levels of height were measured. The coupling coefficient for waves propagating along Z and X crystallographic axes was determined using the measured and calculated results. It has been shown that if the width of incident acoustic beam is quite narrower than the width of periodic structure, then a kind of channelization takes place for the incident wave, and a resonant enhancement of transmission coefficient arises near the center frequency of Bragg stop band.