Abstract :
Summary form only given, as follows. Recent advances in nonlinear optics of liquid crystals (LC) are related to optically induced collective molecular reorientation processes, which account for non-resonant but huge nonlinearities. Those processes exhibit such spectacular features as propagation-induced reorientation, self-oscillations, etc. Jumps and hysteresises of LC´s orientational state with changing incidence angle and intensity of light provides new schemes for optical bistability and opto -optical modulation. In certain circumstances, direct orientational interaction may be conquered by absorption-induced effects. Among several mechanisms to transform the energy of absorbed light beam into molecular reorientation, the strongest one utilizes generation of hydrodynamic motions. In this way, e.g., infrared-visible modulation turns out to be possible at microwatt power level. Thermally induced reorientation in cholesteric LC (CLC), resulting in its helix pitch change, is able to lead to a new effect of light wave tunneling through CLC´s Bragg reflection region. A nonlinear resonator can be designed with intensity dependent reflection coefficients of CLC-mirrors. Thermal indexing itself can have remarkable contribution to nonlinear optics of LC. It provides, in particular, the effect of stationar energy exchange between two equal-frequency light waves through media with local and instantaneous nonlinear response. Thus degenerate wave mixing and beam cleaning turns out to be possible with only two incidence beams.
