Degenerate four-wave mixing in isotropic nonlinear-optical gyrotropic media

An analysis of degenerate four-wave mixing in gyrotropic media is presented. Both natural optical activity and the Faraday effect are considered. A phenomenological expression for the relevant nonlinear polarization, including photoinduced-gyrotropy contributions, in an isotropic medium is derived by use of perturbation theory and isotropic averaging. The coupled wave equations are obtained, and the polarization properties of the generated signal are examined. It is found that the photoinduced-gyrotropy processes can be decoupled from the Kerr effects when the ellipticity of the reflected beam is measured. (C) 1997 Optical Society of America.