SPECTRAL GAPS FOR CLASSICAL WAVES IN PERIODIC STRUCTURES

Recently, the problem of a classical wave (CW), such as electromagnetic (EM), acoustic scalar (AS), or elastic (EL), propagating in composite media, has received increasing interest (Sheng, 1990). In these media, problems, such as electron-electron and electron-phonon interactions which occur in the electronic case, do not exist. For this reason, it is easier to understand and study phenomena of localization. Also, future useful devices may be based on the problem of classical wave propagation (John, 1988; Yablonovitch, 1987; John, 1991).