Rotatory Power And Optical Modulation Of Liquid Crystals

Birefringence and rotatory power are two important parameters for optical modulation by liquid crystals. A new technique has been developed for birefringence measurements at any wavelength in the ultraviolet, visible or infrared spectral regions. The enhanced birefringence of some liquid crystals in the infrared region indicates that these materials will be useful for electro-optic applications in this region. Rotatory power of 90° twisted nematic liquid crystals was measured and found to be in very good agreement with theoretical calculations for a wide spectral range and for different liquid crystal thicknesses. A quantitative relationship between liquid crystal birefringence, wavelength and cell thickness was derived for use in the design of IR liquid crystal light valves with high contrast ratios and minimum response times.