Some Light-Induced Orientational Effects in Nematic Liquid Crystals

Some new light-induced orientational-hydrodynamical nonlinear optical effects in nematic liquid crystals (NLC) are presented. Among them jump-like light-induced hydrodynamic reorientation caused by direct volume expansion, thermomechanical oscillations in hybrid NLC and thermomechanical mechanism of orientational optical nonlinearity in twist aligned NLC as well as in azobenzene liquid crystals. It is also shown that the orientational optical nonlinearity of revealed thermomechanical effect may be as strong as well-known giant optical nonlinearity. Besides, at normal incidence of laser the giant optical nonlinearity does not exist, but thermomechanical effect exists at any angle of incidence of laser radiation and the nonlinearity of thermomechanical effect remains in the same order.