Mode sorter designed for (de)multiplexing vector vortex modes

Mode-division multiplexing is significant in optical communications, and a vector vortex beams (VVBs) set is one of the candidates of the orthogonal set. Although a basic (de)multiplexing scheme has been promoted, there is still a great potential to enable more VVBs with high efficiency. In this work, we promote a vector vortex mode sorter based on a Sagnac interferometer and Q-plate to solve the problem. The Sagnac interferometer acts as a sorter according to |ℓ|, and the Q-plate takes an effect on the shift of indices m. Since our scheme is achieved by the coupling between polarization and orbital angular momentum, it is also suitable for realizing single-photon multi-qubit encoding in quantum information and quantum communications.