Free-space information transfer using the elliptic vortex beam with fractional topological charge

In this paper an elliptic vortex beam with fractional topological charge, which is abbreviated as fEVB, is proposed and applied for the free-space optical communications. A method is also proposed to identify the orbital angular momentum (OAM) states of the fEVBs from the shapes and positions of the intensity distributions of the beams in the receiver unit. The fEVBs would have high information capacity and security level in the free-space information transferring as the fEVBs can have much more OAM states than the conventional vortex beams. The simulation results show that the fractional topological charges of the fEVBs can be decoded precisely with the proposed method.