Completely Spin-Decoupled Dual-Phase Hybrid Metasurfaces for Arbitrary Wavefront Control

Controlling light with a thin flat device is highly desirable in modern optics. A particular prospect in this area is a metasurface that independently shows distinct functionalities for different kinds of incoming waves. However, to date this is mostly achieved on anisotropic metasurfaces based on different propagation phases under two orthogonal linear polarizations. On the other hand, achieving multifunctionality for the two circularly polarized (CP) waves is very important in view of the growing significance of spin photonics. However, achieving completely decoupled optical functions for different photon spins is very challenging and remains elusive. Available attempts were only confined to locked spin-flipped phase profile to achieve opposite vortex modes, converged/diverged focusing, and interchanged holographic images. Here, we propose a general strategy to break this limitation by involving hybrid geometric and propagation phases with extremely low polarization cross-talk (an order of magnitude suppression). We experimentally demonstrate our scheme with two versatile CP bifunctional devices operating at microwaves. Besides, the possible applications have been illustrated from the perspective of stealth and information entropy by imposing dual irregular phase patterns in two completely decoupled helicity channels. The finding in this study is expected to trigger great interest in electromagnetic/optical integration and complex electromagnetic wave manipulations with a new degree of freedom.