Broadband spin-decoupled metasurface for independent wavefront manipulations of orthogonal circularly-polarized waves

Metasurfaces endowed with spin-decoupled functionalities offer the capability to meticulously customize the electromagnetic wavefronts of incident dual orthogonal circularly-polarized (CP) waves in a desirable manner, that holds immense potential for broadening their application fields. Nevertheless, a major lack that persists in most spin-decoupled metasurfaces is the limited bandwidth or the intricate design requirements. Herein, we propose a broadband spin-decoupled metasurface, consisted of weak-resonant mirror-symmetry unit structures, that enables independent and distinct wavefront manipulations under the incidence of orthogonal CP waves. As a demonstration, we present a dual-channel metasurface that integrates geometric and propagation phases to generate vortex waves with two distinct modes in a wide frequency range from 10 GHz to 16 GHz. Both simulated and experimental results are consistent and collectively confirm the validity of our proposed metasurface. The research provides a practical and efficient avenue for constructing spin-decoupled metasurface within a broad frequency band.