Abstract
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.
Highlights
Since the work of Allen et al [1] on the existence of optical orbital angular momentum (OAM) in the light beams with spiral wave fronts, numerous schemes have been demonstrated theoretically and experimentally in the generation, manipulation and detection of OAM beams [2,3,4]
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 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
Summary
Since the work of Allen et al [1] on the existence of optical orbital angular momentum (OAM) in the light beams with spiral wave fronts, numerous schemes have been demonstrated theoretically and experimentally in the generation, manipulation and detection of OAM beams [2,3,4]. We experimentally confirm the rules by which the same coupling mechanism can be used for reception of OAM states, i.e., to detect the total angular momentum (TAM) of an incoming beam and to efficiently collect its energy Since this device is operating in the complete (spin and orbital) angular momentum space [21], it can be deployed as the OAM decoding/de-multiplexing component in OAM fiber transmission systems, or free space transmission links seeded by integrated optical vortex emitters of the similar geometry [1820], without the need of manipulation in polarization states of light. This receiver spares the need for careful calibration on the phase-sensitive waveguides required for the arrayed waveguide and star-coupler based receivers [14, 18], and offers a simpler configuration and more robust mode selectivity of OAM beams
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