Tunnelling of orbital angular momentum in parallel optical waveguides

We study the evolution of circularly polarized optical vortices (OVs) in the system of two coupled few-mode optical fibres.We demonstrate that upon propagation OVs tunnel into the adjacent fibre as a complex superposition of OVs that comprise also OVs of opposite polarization and topological charge.The initial OV may tunnel into the other fibre as the same vortex state of lesser energy.The evolution of the orbital angular momentum in coupled fibres is studied.