Independent optical vortices in free-space optical communications

We present a free space optical communicator prototype working with independent optical vortex beams. The information is encoded by these helical beams which carry different orbital angular momentum (OAM) being superposed in one single channel of communication. The detection consists in the transformation of an optical vortex into a Gaussian beam. This versatile experimental set-up uses reflective spiral phase plates (SPPs) in the transmitter in order to generate the optical vortices. In the receiver an amplitude fork-like computer generated hologram (CGH) detects the transmitted symbols through free space. Simulation results based on Kirchhoff diffraction integral are in agreement with experimental data.