Localized modes and classical wave spectral gaps

An alternate class of spectral gap materials based on the idea of localized modes was presented. The gaps in these materials were created by local resonances and by the fabrication of very compact spectral gap crystals. For photonic crystal, robust photonic gaps excited in any periodic structure was built by using a metal or metal-coated spheres. The frequency and the size of the gaps was found to be dependent on the local order rather than on the symmetry or on the global long range order. For sonic crystals complete sonic gaps with a lattice constant two orders of magnitude smaller than relevant wavelength was studied.