Direct detection receiver for vortex beam.

We present the theory of a direct detection receiver for vortex beams for an optical wireless communication system. The proposed receiver has an array of annular detectors, which enables analysis of power distribution of the vortex beam. We give a detailed description, numerical optimization, and different options for its design. One possible application of this receiver could be high security communication systems, and another could be intra data center communication. Using a given set of parameters, we find that a seven-ring symmetrically spaced detector is comparable to a three-ring detector with an optimized ring area.