Non-selective reflection broadening of a cholesteric liquid crystal at oblique incidence

Abstract

Cholesteric liquid crystals (CLCs) are one-dimensional chiral photonic crystals known for their high tunability. Due to the chirality of the helical superstructure, CLCs exhibit selective Bragg reflection, reflecting only the circular polarization that matches the handedness of the CLC at normal incidence. This characteristic limits the optical performance of CLCs. The total reflection of both circular polarizations (right- and left-handed) can be observed in CLCs at large oblique incidences. However, the narrow bandwidth of this total reflection limits its applications. In this work, we propose a CLC layer with asymmetrical alignment layers to achieve stable bandwidth broadening of the CLC at oblique incidence. The total reflection of both circular polarizations in the CLC is examined experimentally. Compared to conventional planar CLCs, a fourfold increase in the total reflection bandwidth is observed using the proposed method. Additionally, the tunability of the proposed broadening CLC is demonstrated.