Active circular dichroism coding meta-mirror for flexible beam-forming and dynamic amplitude control

Abstract

Equipped with the capability of simultaneous phase and amplitude modulation, the chiral metasurfaces have broken through the weak chiroptical responses of natural media, giving birth to a number of unprecedented phenomena. However, the performance of passive metasurface is inadequate to realize dynamic manipulation to fit the diverse and changeable operation requirements, which would damage their engineering applications. Here, a circular dichroism meta-mirror consisting of Archimedean spiral-based meta-atoms is proposed to achieve dynamic scattering modulation. Combining the strategy of loading active element, the chiroptical responses of a metasurface is smoothly controlled. By controlling bias voltages, continuous scattered reflection amplitude steering can be achieved for the designated spin state while the orthogonal spin state can hardly be influenced. With the assistance of Pancharatnam-Berry phase principle, the metasurface possesses the capability of tailoring waves in coded manner. We experimentally verify the proposed strategy by a 1-bit checkerboard meta-mirror for four-beam scattering pattern. Importantly, the proposed paradigm may find applications in spin-sensitive systems and adaptive camouflage.