Changes in the polarization properties of an electromagnetic wave caused by atoms in external fields

A theoretical analysis is made of changes in the polarization parameters of an electromagnetic wave as a result of its passage through a medium with an anisotropic refractive index. Formulas are obtained for the transformation of the Stokes parameters corresponding to the Faraday, Cotton–Mouton, and Kerr effects in a partly polarized wave. A study is made of changes in the polarization parameters of a weak wave in the presence of strong radiation. The rotation of the polarization ellipse of strong radiation in a nonlinear isotropic medium is discussed. Nonlinear susceptibilities governing the cited effects are calculated for atomic gases by the model pseudopotential method.