Design and evaluation of omnidirectional one-dimensional photonic crystals

Abstract

We have theoretically and experimentally studied a wide range of realistic fabrication parameters for the formation of omnidirectional photonic band gaps (PBGs) in one-dimensional photonic crystals (1D PCs). Photonic band structures in 1D PCs have been analyzed for the cases with and without a defect layer. It is shown that a defect state in the defect-mode PBG behaves like an electronic impurity level in the gap with a change in thickness (i.e., optical path) of the defect layer. Three types of 1D PC structures (Te/polystyrene, Si/SiO2, and ZnS/SiO2), which are designed for applications in the infrared region (especially for the wavelength of 1.55 μm) and in the visible region, are proposed and demonstrated their high reflectance (R) properties experimentally. For example, a six-pair Si/SiO2 1D PC fabricated with a structure parameter (period=388.5 nm, filling factor=0.406) exhibits a wide range omni-PBGs in the wavelength range of 1310–1742 nm. The measured R spectra are in very good agreement with calculated results. In particular, the R spectra of a ZnS/SiO2 1D PC in the wavelength range of 190–800 nm are almost the same as those calculated using complex refractive indices. We also propose conditions to obtain omni-PBGs and band structures for a high refractive-index ambient medium (n).