Photonic defect modes in cholesteric liquid crystal with a resonant nanocomposite layer and a twist defect

Abstract: We have studied spectral properties of a cholesteric liquid crystal with a combined defect consisting of a nanocomposite layer and a twist. The nanocomposite layer is made of metallic nanoballs dispersed in a transparent matrix and featuring effective resonant permittivity. A solution has been found for the transmission spectrum of circularly polarized waves in the structure. We have analyzed spectral splitting of the defect mode in the bandgap of the cholesteric when its frequency coincides with the nanocomposite resonant frequency. Defect modes have characteristics strongly dependent on the magnitude and direction of the phase jump at the interface between nanocomposite and cholesteric layers. It has been found that the bandgap width and the position and localization degree of defect modes can be effectively controlled by external fields applied to cholesteric.