Dynamics of field dislocations and disclinations in a few-mode optical fiber. III. Circularly polarized CP¹¹ modes and L disclinations

Abstract

It has been found experimentally and theoretically that when a stepped-index few-mode optical fiber is excited by a circularly polarized Gaussian beam, linearly polarized pure edge L _x and L _y disclinations are generated in the guided wave fields. The azimuths of the linear polarization of these disclinations rotate in the direction opposite to the rotation of the disclination axes. When the axes of the L _x and L _y disclinations are mutually orthogonal, a pure screw dislocation is created. When the axes are collinear, the L _x and L _y disclinations annihilate and a pure uniform circularly polarized edge dislocation is generated, its axis coinciding with the axis of the disclinations. Reversal of the circular polarization of the excitation changes the sign of the angles of orientation of the pure edge dislocations and disclinations, and also reverses the azimuth of the linear polarization and reverses the sign of the topological charge of the pure screw dislocation. The physical mechanism for the rotation of the disclination and dislocation axes is attributed to the optical Magnus effect in a few-mode fiber. The rotation of the plane of polarization of the L _x and L _y disclinations and the screw dislocation reflects the appearance of the Berry topological phase accompanied by a cyclic change in the orientation of these disclination axes.