II Nonlinear Optics of Liquid Crystals

This chapter discusses the nonlinear optics of the liquid crystals. The mechanisms for optically induced refractive index change in the nematic phase of liquid crystals, and related nonlinear optical processes such as optical wave mixings, self-focusing, and bistabilities are discussed. Liquid crystals are composed of large organic molecules with a typical chemical structure. As a result of intermolecular forces, the molecules tend to align themselves in some fixed direction. Most liquid crystal molecules are uniaxial, centrosymmetrical and nonpolar, although there is a class of liquid crystals that is ferroelectric and possesses large permanent dipole moments. The chapter focuses on selected nonlinear processes in which the extraordinarily large nonlinearity of liquid crystals has shed new light on the fundamental understanding of them, on processes that are on the threshold of being applicable to practical devices, and on special processes that can be obtained only with highly nonlinear materials.