Polarization-dependent orbital angular momentum flipping in fibers with acousto-optic interaction

In this paper we consider the evolution of linearly polarized optical vortices in circular optical fibers with a propagating fundamental flexural acoustic wave. A new polarization-dependent mode conversion is found out, in which the sign of the topological charge (and orbital angular momentum) of the outgoing vortex beam is governed by the direction of the incident linear polarization. This effect can be used for implementing polarization-controlled orbital angular momentum flipping. This paves the way to implementation of the all-fibre stable controlled-NOT gate, in which the linear polarization carries the control qubit and the topological charge carries the target. Such a gate is able to produce optical beams with entanglement between polarization and orbital degrees of freedom in regime of linear optics. Yet, such orbital angular momentum controlling should be useful in micromechanics, classical and quantum information encoding, and classical simulation of quantum algorithms. (paper)