Ordinary and Extraordinary Rays in Gradient-Index Lenses

We assume that the polarization modes of a gradient-index medium with circular cylindrical symmetry are radial and tangential. Making use of a ray-optics method developed for anisotropic crystals, we relate the polarization modes with the permittivity and the dielectric tensor constant of the medium. The polarized imaging response of gradient-index lenses is used to associate ordinary rays with the tangential mode and extraordinary rays with the radial mode. The polarization-mode description is in agreement with the experimental results here. These experimental results allow extending the mode description developed for meridional rays to include skew rays.