Broadband Detection of Multiple Spin and Orbital Angular Momenta via Dielectric Metasurface

Light beams carrying spin angular momentum (SAM) and orbital angular momentum (OAM) have created novel opportunities in the areas of optical communications, imaging, micromanipulation, and quantum optics. However, complex optical setups are required to simultaneously manipulate, measure, and analyze these states, which significantly limit system integration. Here, a detection approach is introduced for measuring multiple SAM and OAM modes simultaneously through a planar nanophotonic demultiplexer based on an all-dielectric metasurface. Coaxial light beams carrying multiple SAM and OAM states of light upon transmission through the demultiplexer are spatially separated into a range of vortex beams with different topological charge, each propagating along a specific wavevector. The broadband response and momentum conservation further enable the demultiplexer to achieve wavelength demultiplexing. The ultracompact multifunctional architecture is envisioned to enable simultaneous manipulation and measurement of polarization and spin encoded photon states with applications in integrated quantum optics and optical communications.