Light Processing and Optical Devices Using Nano-Sized Droplets of Liquid Crystal Dispersed in Polymer

A polymer containing fine droplets of liquid crystal (LC) smaller than 100 nm was investigated for use as an electro-optic material. Two light-processing methods using LC droplets were achieved by making the direction of an applied electric field perpendicular or parallel to the light beam. One method was used to construct a variable retarder, and the other was used to make a phase modulator. First, a prepolymer and bulk LC were mixed; then strong UV irradiation was used to induce photo-polymerization, which resulted in quick phase separation and fine LC droplets. The high density of fine droplets created a large electro-optic effect with a low propagation loss. A halfwave voltage of 45 V, equivalent to an electric field of 2.3 V/pRm, was achieved in the variable retarder. The phase modulator showed a polarization-independent phase shift larger than Ar, which corresponds to a refractive index change of 0.019, when 16 V/pm was applied.