Spin Photonics‐Based on a Twinning Hyperbolic Metamaterial

Abstract Routing and multiplexing of the optical surface waves are critical for the ultra‐compact nano‐photonic systems. Given this background, traditional metal‐based systems, despite of the ability of supporting the surface plasmon polariton propagation, are constrained on manipulations due to the optical isotropy, and artificially designed structures are always required at the input or output to help attain the additional selectivity. Here, a spin‐dependent multi‐channel scheme is proposed based on the modulation ability of the hyperbolic metamaterial's anisotropy on Dyakonov Surface Waves. The input coupling, propagation direction, as well as the output coupling of the optical single are well determined by the certain spin feature carried by the light and the orientation of the interface's anisotropy because of the spin‐momentum locking. Specially, by constructing a twinning hyperbolic metamaterial, which contains the structural symmetry and materials symmetry, a photonic chip with 4 routing channels are demonstrated experimentally, where the spin of an incident beam can be maintained during the propagation on‐chip and then delivered back into the free space, offering a new planar scheme for metamaterial‐based spin‐controlled nano‐photonic applications.