Beam shift in a graded-index optical fiber

The influence of polarization of a light beam on its geometrical characteristics at propagation in a two-dimensional isotropic graded-index medium using the methods of coherent states is investigated. In a paraxial approximation taking into account the second order terms in a vector wave equation, the expressions for the trajectory and width of linearly and circularly polarized radiation are obtained. It is shown that the circular polarization leads to the rotation of the propagation plane of the meridional rays and additional rotation of sagittal rays, depending on the axial shift of the incident beam. Both circular and linear polarizations result in oscillations of the width of a light beam propagating in a graded-index fiber. In the case of linearly polarized light, the initially symmetric beam becomes elliptical with broadening in the direction of the polarization plane. Beam shifts or corrections with respect to geometrical optics caused by the scalar (nonparaxiality) and vector (polarization) wave effects are investigated.