Photonic Crystals based on Cholesteric Liquid Crystals

Bragg reflection for the circularly polarized light is one of the most attractive properties of Cholesteric Liquid Crystal (CLC), which results in its intrinsic ID chiral structure [1]. This property has been already exploited in various applications such as reflective displays, with leading contributions from Kent State University. It is also possible to use the CLC ordered structure (in the planar Grandjean configuration) to create 2D diffraction gratings, by applying electric field to the material [2]-[3]. We propose a new application for this material: by applying a periodic electric field, we generate 2D periodic structures in the bulk, which result in a photonic crystal (PCLC). Such a structure has some decisive advantages with respect to photonic crystals obtained by common holographic methods [4]. High efficiency is one of them, due to the intrinsic efficiency of CLC Bragg mirrors. Another is the reconfiguration capability, as the optical response of PCLC changes as a function of the period and of the applied electric field value.