Study on Optical Properties and Applications of Liquid Crystals in Long Wavelength Regions

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1. Optical properties of nematic liquid crystals and their applications in infrared regions(1) Measurement systems for the properties of nematic liquid crystals in infrared regions are constructed and transmission spectra of several substrates and liquid crystal materials are measured and evaluated.(2) Birefringence properties of nematic liquid crystals are measured by using transmission properties in homogeneously aligned liquid crystal cells under a voltage application or the light transmission intensity ratios of an ordinary and extraordinary ray.(3) As electrooptical effects of nematic liquid crystals, TN effects in the infrared region, electrooptical effects in absorption band of liquid crystals, polarization controlling effects by the liquid crystal cells with an axially symmetrical molecular orientation, and light scattering effects in infrared regions by liquid crystal microlens arrays are measured and discussed.2. Optical properties of nematic liquid crystals and their applications in submillimeter wavelength regions(1) Transmission properties at the wavelengths of 118,215 and 435 [mum] are measured by using a CH_2F_2 submillimeter wave laser that is excited by a CO_2 laser. Refractive indices for ordinary and extraordinary ray are measured by changing the tilt angle of homogeneously aligned liquid crystal cells. Absorption effects can be ignored since the liquid crystal layr is effectively thin.(2) Transmittance of the liquid crystal microlens array cell can be modulated for about 30 [%] by applying a voltage across the cell. Phase change of lambda/8-lambda/10 (lambda=118 [mum]) corresponding to the birefringence of 0.12-0.15 can be obtained in the homogeneously aligned liquid crystal (K15) cell by applying a voltage.