Optically transparent and wideband absorption-tunable metasurface based on patterned graphene

In this paper, a patterned graphene-based metasurface absorber (PGMA) with optical transparency, high absorption performance, a large tunable absorptivity range, and extremely wide angular stability is proposed. Such a tunable metasurface is achieved by loading a patterned graphene sandwich on a patterned indium tin oxide (ITO) structure with a polymethyl methacrylate (PMMA) substrate and an ITO ground plane. When controlling the bias voltage between two graphene sheets from 0 to 6 V, the absorptivity of the proposed metasurface can be tuned from above 0.9 to 0.6 over the wide frequency range of 7.8 GHz to 12.5 GHz. Meanwhile, the tunable absorptivity range peaks at 0.38 around 9.28 GHz. Additionally, subwavelength unit cells are adopted to ensure that the electromagnetic (EM) response of this design is stable up to 65° oblique incidence. The wideband tuning mechanism is demonstrated by numerical simulation, an equivalent transmission line (ETL) model, and experiment. This design may have manifold applications, such as EM shielding and camouflage.