Geometric Phases in Optics: Polarization of Light Propagating in Helical Optical Fibers

The geometric phase in optics (GPIO) is directly associated with the polarization of light. We investigate the physical principles underlying the occurrence of the GPIO for a single-mode light beam propagating in a single-mode optical fiber wound into a circular helix configuration, with and without stress-induced birefringence. The effects of the curvature and torsion of the helical fiber on the rotation of the polarization vector and the associated GPIO are discussed. Analytic expressions are derived for the polarization vector and Stokes parameters for any initial polarization state of the light entering the helical fiber, as well as for the GPIO of the light as a function of helix arc-length. Additionally, the intensity of a superposition of the initial and final beams, which depends on the final GPIO, is derived. Furthermore, the relationship between the GPIO and the solid angle subtended by the tangent vector of the helix plotted on the Poincaré sphere is analyzed, and the effects of fluctuations of the parameters specifying the geometry and the material characteristics of the helical fiber on the GPIO are considered.