Diodelike Spin-Orbit Interactions of Light in Chiral Metasurfaces

Diodelike spin-orbit interactions (SOIs) of light at metasurfaces bring novel functionalities to optical devices but have never been achieved so far. In this paper, we experimentally demonstrate a diodelike asymmetric metadevice that exhibits asymmetric SOIs of light in chiral metasurfaces. The exploited physical mechanism is based on the maximization of the polarization conversion for a designated circularly polarized light in transmission. Chiral metaatoms are employed to enhance the interaction between spin angular momentum and matter, while phase discontinuities are introduced at the interface for helicity-dependent generation of orbital angular momentum. Three proof-of-concept metasurfaces that demonstrate asymmetric circular polarization conversion, asymmetric spin deflection, and asymmetric spin-to-vortex conversion are designed, fabricated, and experimentally characterized, respectively. Compared with the Faraday effect under the external magnetic field, the designer metasurfaces here are all reciprocal and offering asymmetric angular momentum division with high efficiency. Our findings provide the possibility of asymmetric multifunctional metadevices for high-performance on-chip parallel multiplexing.