Parallel Detection of OAM States Carried by Coaxial Bessel Beams

We propose and demonstrate an optical vortex Dammann axicon grating to simultaneously detect coaxial high-order Bessel beams. The coaxial superposition of multiple Bessel beams are spatially separated and converted into light spots by the grating according to their carried orbital angular momentum (OAM) states. The self-healing property of the Bessel beams is verified for single and multiple Bessel beams in terms of the OAM states detection. We also quantitatively measure that the OAM has a mode purity of 96% with obstacle.