Graphene-Based Tunable Metasurface Screen with Fresnel Zone Resonators (FZRs)

Abstract

Metasurfaces, which can create phase jumps to control the reflection and refraction of light, are the updated versions of metamaterials for optical frequencies. Snell's law follows the surface phase distribution anomalously which constituted achievements decade ago that were highly significant by means of wavefront manipulation. One of these achievements was real holography which has been accomplished several times by the usage of metasurfaces. They can even be controlled digitally to create dynamic holographic images floating in the air. The applications involving metasurface holography up until today using anomalous reflection and refraction to focus wave fronts and create images suffer from relatively small image and focal length. Alternatively, Fresnel zone plates (FZPs) are known to focus light can be used to focus individual pixels which would only require a binary information. So that they can be adopted to construct 3D digital images by located individual pixels and/or voxels in air. Unfortunately, for the focusing effect to take place, Fresnel zone sizes should be at micron scale which also constitutes a micron scale focusing. Luckily, the focus length can be extended by sophisticated electric field excitations and once a single, bilayer or multilayer graphene sheets are used as the inclusions, tuning quality may improve. Therefore, if an array of these is used to construct a metasurface, the collective response may provide better focusing characteristics. As an ongoing study, we propose a topological idea for a tunable metasurface with inclusion which we called as Fresnel zone resonators (FZRs) - even if they do not actually resonate - that implement FZP topology. At the end, an electronically controllable screen of the proposed FZR units is discussed by means of phase, scattering dynamics and possible manufacturing processes.