Polarization-controlled topological charge inversion of optical vortices in multielliptical optical fibers

Analytical expressions for higher-order modes with azimuthal number $|\ell|\ge 2$ and their propagation constants for multielliptical optical fibers exhibiting a torsional mechanical stress are obtained in the vicinity of the resonance twist-pitch values. It is demonstrated that the resonance modes represent a superposition of two optical vortices with identical circular polarization and opposite signs of the topological charge. The effect of topological-charge inversion of the output optical vortex controlled by a change of sign of the circular polarization of the input beam is predicted. This effect paves the way to creating a logical CNOT element based on multielliptical fibers.