Observation of Interaction of Spin and Intrinsic Orbital Angular Momentum of Light

TL;DR

This paper reports the experimental observation of the interaction between spin and intrinsic orbital angular momentum of light, demonstrated by length-dependent rotations in a cylindrically-symmetric optical fiber.

Contribution

It provides the first experimental evidence of spin-IOAM interaction in straight optical fibers through mode superpositions and degeneracy splitting.

Findings

Length-dependent rotations of spatial patterns and polarization observed

Interaction occurs in superpositions of modes with parallel and anti-parallel spin and IOAM

Degeneracy splitting of propagation constants causes the observed rotations

Abstract

Interaction of spin and intrinsic orbital angular momentum of light is observed, as evidenced by length-dependent rotations of both spatial patterns and optical polarization in a cylindrically-symmetric isotropic optical fiber. Such rotations occur in straight few-mode fiber when superpositions of two modes with parallel and anti-parallel orientation of spin and intrinsic orbital angular momentum (IOAM=$2\hslash$) are excited, resulting from a degeneracy splitting of the propagation constants of the modes.