Wide-band acoustic collimating by phononic crystal composites

We numerically investigated the collimation phenomena in phononic crystal (PC) composites, a sequenced series of PCs with the same period but different filling ratios. The plane wave expansion (PWE) method was used to obtain the band diagrams and the equal frequency surfaces of both single PCs and PC composites. The finite difference time domain (FDTD) method was then utilized to simulate the propagation of acoustic waves inside a PC composite. The results from both PWE calculations and FDTD simulations show that in comparison to a single PC, a PC composite can significantly enlarge the collimation region and realize wide-band acoustic collimation. (C) 2008 American Institute of Physics.