Photonic structures of metal-coated chiral spheres

A detailed analysis of the optical properties of photonic structures of metal-coated chiral spheres, calculated by the full electrodynamic layer-multiple-scattering method, is presented. Easily tunable narrow bands, originating from particle-like plasmon modes of the metallic shells, hybridize with the extended bands of the underlying effective chiral medium and give rise to sizable partial gaps and strong band bending with consequent negative-slope dispersion. The photonic band diagram is discussed in the light of group theory, in conjunction with relevant transmission spectra, and the occurrence of polarization-selective transmission and negative refraction for a short range of angles of incidence is demonstrated. (C) 2012 Optical Society of America