Orbital Angular Momentum (OAM) Carried by Asymmetric Vortex Beams for Wireless Communications: Theory, Experiment and Current Challenges

Unlike traditional symmetrical vortex beams, we demonstrate one kind of asymmetric spatial modes, namely Lommel-Gaussian (LMG) mode carrying orbital angular momentum (OAM) for optical communications, which possesses higher channel capacity through orthogonal multiplexing process. Some unique properties, such as better detection probabilities of high-order modes compared with low-order modes, are experimentally observed and well explained using theoretical models based on Rytov approximation method. An efficient scheme to generate LMG superposition states for OAM mode multicasting and multiplexing is proposed. Also, some critical issues, such as mode mismatching, still need further investigations. This work inspires us to explore more spatial multiplexing approaches, whose distinctive properties may open up new prospects for future communications systems.