Measurements of Third Order Optical Nonlinearities of Nematic Liquid Crystals

Abstract

Abstract In order to better understand the physical mechanisms responsible for the large observed optical nonlinearities of nematic liquid crystals, we have carried out nonlinear absorption and nonlinear refraction measurements on the pure liquid crystals 5CB and 8CB, and the liquid crystal mixture E7 using picosecond, nanosecond and millisecond pulses. We have used the recently developed Z-scan method1–2, a sensitive single-beam technique which allows the determination of the sign and magnitude of the nonlinear refraction and the magnitude of the nonlinear absorption for aligned samples3. We have performed these measurements on aligned samples at wavelengths of 514nm and 532nm. In addition, we have studied the temperature dependence of the nonlinear refractive indices. Possible mechanisms responsible for the observed nonlinearities are discussed.