Electrically reflectance-tunable circular polarization reflector based on thin polymer-stabilized cholesteric liquid crystals

Abstract

This paper presents a reflectance-tunable circular polarization reflector that utilizes thin polymer-stabilized cholesteric nematic liquid crystals (PSCLCs) with negative anisotropy. The switching mechanism involves direct-current (DC) field-induced movement in the polymer network, which generates the mechanical force that causes a pitch-gradient helical structure and thus a distorted Bragg reflection. The pitch-gradient helical structure of the 5 μm-thick cells only allows for a limited number of pitch lengths, resulting in a decrease in reflectance at the designed Bragg reflectance and a reflectance tunable range determined by applying DC voltages. The PSCLCs reflecting red, green, and blue colors were measured for their reflectance tuning ability and circular polarization selectivity. A tunable polarization volume grating was fabricated using a PSCLC cell, and the ability of the grating to diffract light intensity was demonstrated.