Giant and controllable Goos–Hänchen shift of a reflective beam off a hyperbolic metasurface of polar crystals

We conduct a theoretical analysis of the massive and tunable Goos–Hänchen (GH) shift on a polar crystal covered with periodical black phosphorus (BP)-patches in the THz range. The surface plasmon phonon polaritons (SPPPs), which are coupled by the surface phonon polaritons (SPhPs) and surface plasmon polaritons (SPPs), can greatly increase GH shifts. Based on the in-plane anisotropy of BP, two typical metasurface models are designed and investigated. An enormous GH shift of about −7565.58 λ 0 is achieved by adjusting the physical parameters of the BP-patches. In the designed metasurface structure, the maximum sensitivity accompanying large GH shifts can reach about 6.43 × 10 8 λ 0 /RIU, which is extremely sensitive to the size, carrier density, and layer number of BP. Compared with a traditional surface plasmon resonance sensor, the sensitivity is increased by at least two orders of magnitude. We believe that investigating metasurface-based SPPPs sensors could lead to high-sensitivity biochemical detection applications.