Numerical investigations of transmission and waveguide properties of soniccrystals by finite-difference time-domain method

The novel properties of a "sonic crystal" are investigated and its applicat ion to a new acoustic waveguide are discussed by developing the finite-diff erence time-domain (FDTD) method for acoustic wave propagation in a finite- size periodic structure. A sonic crystal is formally an acoustic version of a "photonic crystal." It is not an actual crystal but an artificial one co mposed of a periodic array of acoustic scatterers imbedded in the host mate rial. and expected to have acoustical band gaps where the acoustic wave can not penetrate the crystal. These properties are numerically investigated, a nd sonic crystals are shown not to be acoustic replicas of photonic crystal s. Interesting artificial crystals which can be realizable as sonic crystal s but not as photonic crystals are realized by clarifying the correspondenc e relationship between the transverse-electric and transverse-magnetic wave s and the longitudinal acoustic wave in the two-dimensional space. Full ban d-gap characteristics versus wavelength and wave propagation in acoustic wa veguides are shown.