Phenomenological model of nonlinear optical properties of a topological medium

Based on the semiclassical description of the dynamics of electrons in topological media, the gyrotropic properties of which are determined by a nonzero Berry curvature, a phenomenological model is proposed that allows one to consider some nonlinear optical processes—the generation of the third harmonic and the intensity dependent rotation of the wave polarization vector. The third-order nonlinear susceptibilities are determined, which determine the interaction of waves with allowance for the rotation of their polarization vector. Gyrotropy manifests itself in the dependence of the efficiency of conversion to the harmonic on the circular polarization of radiation, which can be used to measure the parameters of these media.