Free-space optical transmission with orbital angular momentum division multiplexing
ABSTRACT The experimental demonstration of a free-space optical transmission system with orbital angular momentum (OAM) division multiplexing is reported. Two beams have been multiplexed with different values of the azimuthal index l , and hence carrying different OAM, at a wavelength of 1550 nm. The first beam ( l = 0) is nearly Gaussian and it features an OAM equal to zero. The second beam ( l = 1) is an optical vortex produced by means of a suitable computer-generated hologram, which shows an intensity pattern with a doughnut shape and possesses an OAM of - h per photon. A binary intensity modulation at 1.25 Gbit/s has been applied to each OAM channel and an interferometer with Dove prisms has been exploited for OAM demultiplexing.