We numerically demonstrate broadband optical switches which can control the propagation of mid-infrared waves that is incident to the interface between a switchable hyperbolic metamaterials (SHM) and air. The SHM consists of a one-dimensional periodic stacking of graphene layers and dielectric layers. The isofrequency curve of the structure can be switched between hyperbolic shape and elliptical shape by controlling the external gate voltage or the electrostatic field biasing. It is revealed that when the interface between air and the SHM is parallel to the graphene sheets, it can switch between positive refraction and total reflection; when the interface is perpendicular to the graphene sheets, it can switch between positive and negative refraction.
Published in: "EPL".