Analyses of surface acoustic wave propagation in phononic crystal waveguides using FDTD method

In this paper, we adopt finite difference time domain (FDTD) method to analyze surface acoustic waves propagating in two-dimensional phononic waveguides. To implement the FDTD program for dealing with surface acoustic waves, the Bloch theorem and absorbing boundary conditions are employed to deal with the periodic boundary condition and reflection from a numerical boundary. A phononic crystal consisting of circular tungsten cylinders which form a square lattice in a silicon matrix is analyzed in this study. The dispersion relation and displacement fields are calculated to identify the band gaps and eigenmodes. The result shows the existence of a total band gap of surface waves and thus an acoustic waveguide is created accordingly. The analysis shows a confined propagation of the surface waves inside the waveguide.