Recovery of the topological charge of a vortex beam propagated through a scattering layer

Coherent vortex beams have shown great potential in many applications including information transmission under non-ideal conditions, as information can be encoded in the orbital angular momentum. However, inhomogeneity of atmosphere tends to scramble the vortex structure and give rise to speckle. It is therefore of great interest to reconstruct the topological charge of a vortex beam after it propagates through a scattering medium. Here, we propose a feasible solution for this. The proposed method measures holographically the scattered field and reconstructs the spiral phase from it by taking advantage of both the deterministic nature and the ergodicity of the scattering process. Our preliminary experiments show promising results and suggest that the proposed method can have great potential in information transmission under non-ideal conditions.