Polarization-Induced Interaction as a Perturbation within Orbital Angular Momentum(OAM) Modes of an Optical Fiber (2108.08280v1)

Abstract: We investigate the role of polarization effects in orbital angular momentum modes of an optical fiber. Specifically, we revisit the removal of the degeneracy of the $HE$ and the $EH$ vector modes that exists within the weakly guiding approximation (WGA); within WGA, these two vector modes coalesce into a single spatial (scalar) orbital angular momentum (OAM) mode, defined by a common topological charge and associated with left or right circular polarization. While the polarization term of the vector wave equation acting as a Hermitian perturbation operator accounts for the splitting of the $HE$ and the $EH$ vector modes, its extension to explain the accompanying field correction, called the polarization-induced field, encounters hurdles; this field is characterized by a topological charge differing by two in magnitude. The problems are critically examined with a possible remedy and its implications.