High-efficiency and Wideband five-order Geometric-Phase Coding Metasurfaces for Sub-terahertz RCS Reduction

Pancharatnam-Berry principled high-order geometric-phase metasurfaces have drawn considerable interest for their unique ability to regulate electromagnetic waves exquisitely. However, the efficiency and bandwidth of high-order geometric-phase metasurfaces remain to grapple with for practical applications. Herein, we propose a high-efficiency and wideband five-order geometric-phase coding metasurface consisting of 5-fold rotationally symmetric structures. Rotating the proposed meta-atoms can effectively realize LCP-RCP conversion over 90% efficiency in 105-120 GHz or vice versa and 2-bit coding with smooth pi/2 phase-shift interval. As a proof of concept, a 2-bit high-order geometric-phase coding sequence convoluted from the cross-coding and orthogonal coding sequences attains enhanced RCS reduction on the proposed metasurface. Corroborated by rigorous full-wave simulations and numerical calculations, the novel phase-coding metasurfaces are promising in terahertz holograms, computational imaging, vortex beam generations, flat lenses, etc.