Photonic band gaps and flat band edges in periodically textured metallic microcavities

The dispersion of optical modes in metallic microcavities is shown to be dramatically altered when wavelength-scale periodic texture is added to one of the cavity mirrors. We demonstrate that Bragg scattering of the cavity modes by such microstructure produces near-flat bands that remain significantly flat well away from the first Brillouin zone boundary. The electric fields associated with these modes are studied and are found to have field maxima that are enhanced over those pertaining to planar microcavities. The impact of this band structure upon emissive devices, especially in terms of the clear insensitivity to viewing angle, is discussed.