Light selective reflection asymmetry in cholesteric layer with planar–conical anchoring

Abstract

The orientational structure and spectral properties of a cholesteric layer with planar–conical boundary conditions are studied. Initially, a structure with circular-shaped domains characterized by double twisting of the surface linear defect is formed. Under the influence of an electric field, the domains take the shape of polygons. This system has an asymmetric selective reflection of light: the reflection of right-circularly polarized light close to 100% is observed at a normal incidence of radiation on the sample from the planar boundary conditions, while a selective reflection of light does not occur for radiation incident from the conical anchoring. The light transmission of the sample in the forward direction does not depend on which substrate the radiation falls on. This spectral behaviour is due to the peculiarity of the formation of the domain structure in the cholesteric layer, in which the circular domains are initially located only near the substrate with a conical anchoring. A practically uniform planar cholesteric structure is formed near another substrate with planar boundary conditions. The selective reflection asymmetry is reduced by an applied voltage in the range of 0 to 12 V. The cholesteric transforms into a scattering state at an applied voltage of 12 V $<U<72$ V and becomes a transparent at $U>72$ V. Switching off the electric field, under the influence of which the cholesteric is in a transparent state, leads to the restoration of the asymmetry of selective light reflection.