Optical components are designed and fabricated by using liquid crystals.
Left handed circular polarizer for 632.8 nm was designed and made with the mixture of ZLI-1167 (66.81%) and CB15 (33.19%). For this purpose, center wavelength of the selective reflection band (SRB) of two cholesteric mixtures, E7 with CB15 and ZLI-1167 with CB15 was examined for various weight fractions of CB15 in the mixture. The ellipticity of the elliptical polarization of the transmitted light was 0.98.
Both passive and active liquid crystal waveplates were made utilizing the uniaxial property of nematic liquid crystal ZLI-2244-100 (Merck). In the case of passive liquid crystal waveplate, the cell gap was set by using ZnS thin film islands deposited with vacuum coating through monitoring the reflected light from the glass substrate and the coat surface to give the accurate retardation value. Active liquid crystal waveplate can be tuned by adjusting the birefringence with the applied AC electric field. Threshold voltage for Freedericksz transition was about 3.27 volts (peak amplitude of 2kHz square wave) and the half-wave voltage and quarter-wave voltage for 632.8 nm were 3.746 volts and 5.891 volts, respectively (at $20 \pm 0.5^\circ\mbox{C}$). We tested the LC waveplates by using the Fast Fourier Transform method. Retardation value was found to be $89.5 \pm 2.5^\circ$ and $90.3 \pm 4.0^\circ$ for passive and active quarter waveplate respectively, and $180.5 \pm 5.0^\circ$ for active half waveplate. Active waveplate was used as a phase shifter in a phase shifting Twyman-Green interferometer to test optical components with low applied voltages than other phase shifters such as PZT.
It is demonsrtated that a cholesteric liquid crystal cell placed between two liquid crystal quarter waveplates whose fast axes are orthogonal to each other can function as a linear polarizer. The fabricated LC linear polarizer yielded an extinction of 205:1.
Liquid crystal linear polarizers are expected to be used as large aperture polarizing elements for Faraday optical isolators in a high power laser system.
