Tailoring standing waves on meta-atom: a facile way to a high-efficiency functional metasurface with spin-selectivity

Metasurfaces have provided unprecedented degrees of freedom in manipulating electromagnetic (EM) waves and have been applied in the communication field. Growing communication demands require smaller and more versatile devices. However, there is still a gap in recent miniaturization versatile research. Here, we propose a design method to realize an ultrathin multifunctional metasurface by tailoring standing waves that formed on meta-atom both in longitudinal and transverse dimensions. Firstly, to guarantee high-efficiency coupling between incident waves and meta-atom, we place the metallic pattern at the peak point of longitudinal standing waves which formed by the interferences between incident and reflected waves via adjusting the substrate thickness. Then we can realize the diverse functions for different incident spin states by loading lumped elements at the standing wave peaks or nodes of the transverse surface currents. For this proof-of-concept, we demonstrate a spin-selective vortex beam generation metasurface with an ultrathin thickness 0.144λ₀. The design can generate a vortex beam for right-handed circularly polarized (RHCP) waves with an efficiency above 80% in 14.0-23.0 GHz while it can achieve high absorption above 90% for left-handed circularly polarized (LHCP) waves in 13.8-23.3 GHz. To sum up, this method might help to design spin-selective metasurfaces with multifunctional integration and find applications in satellite communication, EM compatibility and others.