Electro-induced photonic structures in cholesteric and nematic liquid crystals

Abstract

This paper reviews recent research performed at the liquid crystals laboratory of the A. V. Shubnikov Institute of Crystallography, Russian Academy of Sciences, focusing on photonic liquid crystalline structures induced by electric fields. Due to field-induced spatial modulation of the refractive index, such structures exhibit optical properties characteristic of photonic crystals. Two types of structures are discussed. The first type is induced in cholesteric liquid crystals with spontaneous formation of a helical director distribution. The orientation transition to a state with a lying helix – with the axis in the plane of the layer – is considered. The second type consists of homogeneous layers of non-chiral nematic liquid crystals, where the modulation of the refractive index arises due to the flexoelectric instability effect. In both cases, periodic boundary conditions of molecule orientation are crucial. Methods of forming boundary conditions and the photonic properties of structures are reviewed.