Graphene-based hyperbolic metasurfaces

We explore the electromagnetic response of ultrathin metasurfaces realized by densely-packed arrays of graphene strips. We analyze various topologies of propagation bands supported by this structure, ranging from the canalization regime found at a few terahertz (THz), hyperbolic responses present at a few dozens of THz, and anisotropic elliptic TE and TM regimes that arise at mid-infrared frequencies. Interestingly, this configuration can be tuned by exploiting graphene's field effect. We also study the influence of the intrinsic spatial dispersion of graphene, demonstrating that it imposes a wavenumber cutoff on the hyperbolic dispersion diagram that is inversely proportional to the Fermi velocity of electrons in the material. In addition, we show how spatial dispersion limit the maximum enhancement of the spontaneous emission rate of emitters located nearby. Our findings may lead to the development of exciting reconfigurable plasmonic devices with direct application in hyperlenses, sensing, imaging, and on-chip communications.