Hyperbolic spoof plasmonic metasurfaces

Hyperbolic metasurfaces have recently emerged as a new research frontier because of the unprecedented capabilities to manipulate surface plasmon polaritons (SPPs) and many potential applications. However, thus far, the existence of hyperbolic metasurfaces has neither been observed nor predicted at low frequencies because noble metals cannot support SPPs at longer wavelengths. Here, we propose and experimentally demonstrate spoof plasmonic metasurfaces with a hyperbolic dispersion, where the spoof SPPs propagate on complementary H-shaped, perfectly conducting surfaces at low frequencies. Thus, non-divergent diffractions, negative refraction and dispersion-dependent spin-momentum locking are observed as the spoof SPPs travel over the hyperbolic spoof plasmonic metasurfaces (HSPMs). The HSPMs provide fundamental new platforms to explore the propagation and spin of spoof SPPs. They show great capabilities for designing advanced surface wave devices such as spatial multiplexers, focusing and imaging devices, planar hyperlenses, and dispersion-dependent directional couplers, at both microwave and terahertz frequencies. An artificial optical material known as a hyperbolic metasurface that operates at low frequencies has been made. Metamaterials can be designed to have optical properties not found in nature. One example is the hyperbolic metasurface, so called because the strongly anisotropic electric or magnetic response of the material creates a hyperbolic dispersion in the photon's momemtum space. So far, only hyperbolic metasurfaces that operate at relatively high frequencies have been created. Now, Hongsheng Chen from Zhejiang University in China and co-workers has created a spoof plasmonic metasurface with exotic optical properties and that have low-frequency operation. They achieved this by using so-called spoof surface-plasmon polaritons that arise as light interacts with capacitances and inductances created by an array of H-shaped perfectly conducting surfaces. We propose and experimentally demonstrate spoof plasmonic metasurfaces with a hyperbolic dispersion, where the spoof SPPs propagate on complementary H-shaped perfectly conducting surfaces at low frequencies. In this way, non-divergent diffractions, negative refraction, and dispersion-dependent spin-momentum locking are observed as the spoof SPPs travel over the hyperbolic spoof plasmonic metasurfaces. They show great capabilities to design advanced surface wave devices such as spatial multiplexers, focusing and imaging devices, planar hyperlenses, and dispersion-dependent directional couplers, at both microwave and terahertz frequencies.