Bistable spatial light modulator using guest-host liquid crystal and bi₁₂GEO₂₀photoconductive crystal

This paper describes a new bistable spatial light modulator consisting of a guest-host type of 90°-twisted nematic liquid crystal layer and a Bi₁₂GeO₂₀photoconductor. The optical bistability is generated by an internal electro-optic feedback effect based on the nonlinear transmittance property of the guest-host liquid crystal layer and the photoconductive property of the Bii2Ge02o crystal. This device has various optical threshold functions, where the optical threshold level is easily controlled by varying the drive voltage of the device or its frequency. Optical image binarization and optical parallel logic operations based on optical bistability are realized by illuminating the liquid crystal layer with blue light. It has a limiting resolution of 25 lp/mm, and the rise and decay times of the device are approximately 30 ms and 90 ms, respectively.