Broadband all-metal reflective-mode geometric metasurfaces for visible multi‐functional wavefront manipulation

Abstract

Visible light manipulation has become a well-explored subject over recent years owing to its fascinating prospect in the optical communication field. Nevertheless, the limitations imposed by materials inherent in natural hamper the progress of the optical devices. Here, a broadband reflective-mode all-metal geometric metasurface (GMS) capable of high-efficient circular polarization (CP) conversion and applicable for multi-functional wavefront manipulation was proposed and investigated numerically in visible region. The proposed all-metal GMS is comprised of the periodically arranged gold dumbbell-shaped (DBS) nanostructure with symmetrical square notch adhered on the gold substrate. Simulation results demonstrate that the cross-polarized reflection amplitude of the all-metal GMS for normal incident CP light is practically higher than 85% from 310 THz to 500 THz, and the full 2π phase shift in this frequency range can be acquired by varying oriented angle of the DBS nanostructure. As proofs of multi-functional wavefront manipulation devices, beam deflectors, reflective planar focusing metalens and vortex beam generators were constructed and demonstrated numerically with the all-metal DBS nanostructure based on geometric phase principle. Overall, the proposed GMS carries with it considerable advantages of compaction and high efficiency, thus possessing infinite potential in optical devices.