Polarization-Selective On-Chip Orbital Angular Momentum Photon Sources Enabled by Nanodiamond Emitters in Metasurface-Decorated Waveguides

Abstract Encoding light with orbital angular momentum (OAM) provides additional photonic degrees of freedom for optical communications, structured-light engineering, and high-dimensional information processing. However, most OAM platforms rely on externally generated light, separating photon generation from OAM conversion. Here, we demonstrate source-integrated OAM photon generators combining nanodiamond-hosted nitrogen-vacancy emitters, dielectric waveguides, and metasurface-engineered holographic gratings in a chip-scale architecture. Emission from the embedded emitters is coupled into the fundamental waveguide mode, routed on chip, and converted into free-space vortex beams with prescribed helical phase fronts. A polarization-selective four-arm architecture further enables selective generation of OAM beam pairs with topological charges of ±1 and ±2 through control of excitation polarization. Experiments demonstrate high-purity OAM emission in agreement with simulations. This platform integrates photon generation, waveguide transport, and structured-light emission, providing a scalable route toward compact OAM sources and high-dimensional integrated photonic systems.