Orbital angular momentum demultiplexing with synthetic partial aperture receivers

Long-distance transmitted orbital angular momentum (OAM) cannot be received completely by a single aperture receiver due to the divergence of OAM beams in free space, which results in a challenge for measuring and demultiplexing the multi-OAM modes. We propose a novel approach in measuring multi-OAM modes by using synthetic partial aperture receivers, which could significantly reduce the intensity crosstalk caused by a power leakage. The available OAM modes in a long-distance free-space communication system are greatly increased, and all of the OAM modes can be used for multiplexing or encoding. Furthermore, an OAM demultiplexing array is employed to convert the incident OAM modes into Gaussian-like beams that can be detected by commercial photodetectors with high speed. The proposed approach has great potential applications in long-distance free-space OAM detection and communication.