Effect of the spin–orbit interaction on polarization conversion in coupled waveguides

Abstract

A generalization of perturbation theory for weakly coupled optical waveguides beyond the scalar approximation is suggested that explicitly allows for the spin–orbit interaction embedded in the gradient term of the vector wave equation. The obtained perturbation theory is applied to study the problem of cross-talk in coupled ideal monomode fibres. We demonstrate the absence of cross-talk between orthogonal linear polarizations and the inversion of the circular polarization's sign caused by the spin–orbit interaction. The spin conversion length is determined.