Bi-Layer Reflection-Transmission Dual-Mode Metasurface with Flexible Bandwidth Control

A general strategy for designing bi-layer reflection-transmission integrated dual-mode metasurfaces is presented with flexible bandwidth control. The design of such metasurfaces is enlightened by introducing a cutting hole in the ground plane, which not only acts as a filter for reflection and transmission but also has an eloquent role for bandwidth control. For proof of concept, a bi-layer metasurface consisting of split ring resonators (SRRs) is designed on the top side and I-shaped resonators on both sides. The proper adjustment of ground cut/hole shifts the two co-polarized resonances (initial resonances of the SRRs) close to each other, and in addition, converts wideband cross-polarized reflection (in between the two initial co-polarized resonances of SRR) to co-polarized reflection. This results in a broadband response by shifting two co-polarized resonances close to each other and converting cross-polarized reflection into co-polarized reflection. It is demonstrated that a simple SRR can be responsible for broadband (7.9-12 GHz) reflection while an I-shaped structure is used for transmission with central frequency at 17.58 GHz with independent phase controls. To endorse the proposed strategy, a metasurface prototype is fabricated and tested for the generation of vortex beams and focusing. A general strategy is presented for bi-layer reflection-transmission integrated dual-mode metasurfaces with flexible bandwidth control. The proposed strategy enlightened by introducing cutting hole in ground, which not only acts as a filter, but also has an eloquent role for bandwidth control. Independent geometric phase shift for integrated broadband co-polarized reflection and transmission is achieved with simple technique and compact structure. image