A simple and ultra-compact integrated optical vortex beam receiver device is
presented. The device is based on the coupling between the optical vortex modes and
whispering gallery modes in a micro-ring resonator via embedded angular gratings, which
provides the selective reception of optical vortex modes with definitive total angular
momentum (summation of spin and orbital angular momentum) through the phase matching
condition in the coupling process. Experimental characterization confirms the correct
detection of the total angular momentum carried by the vortex beams incident on the device.
In addition, photonic spin-controlled unidirectional excitation of whispering-gallery modes in
the ring receiver is also observed, and utilized to differentiate between left- and right-circular
polarizations and therefore unambiguously identify the orbital angular momentum of incident
light. Such characteristics provide an effective mode-selective receiver for the eigen-modes in
orbital angular momentum fiber transmission where the circularly polarized OAM modes can
be used as data communications channels in multiplexed communications or as photonic
states in quantum information applications