EFFECT OF POLARIZATION SELF-ACTION IN CUBIC-CRYSTALS - PECULIARITIES AND APPLICATIONS

New concepts are developed to describe a wide area of nonlinear system s involving the phase relaxation peculiarities for the degenerate two- level system under the resonant optical excitation. Nonlinear suscepti bility of the two-level system becomes anisotropic, and self-induced c hanges of polarization (SICP) are developed to the large (gigantic) ma gnitudes. The nonlinearities of two different natures are considered: the saturation of absorption and the resonant optical reorientation of anisotropic defects. For these particular cases, the SICP effects man ifest themselves at a field much lower than that in traditional nonlin ear optics. The larger magnitudes of the effects offer good possibilit ies for the development of optical devices based on the new physical p rinciples. Various applications of SICP effects are demonstrated, incl uding the spectroscopic investigations of impure cubic crystals, optic al diagnostics, optical storage, information processing, and the devel opment of new optical devices.