Dynamically Tunable Broadband Infrared Anomalous Refraction Based on Graphene Metasurfaces

Metasurfaces, which are capable of generating structure and wavelength dependent phase shift, have emerged as promising means for controlling the wavefront of electromagnetic waves. Finding new ways to realize broadband frequency response as well as maintaining high conversion efficiency still requires research efforts. For the design of plasmonic metasurfaces, graphene represents an attractive alternative to metals due to its strong field confinement and versatile tunability. Here, a novel metasurface based on graphene is proposed to control the wavefront of light. Dynamically tunable anomalous refraction composed of periodically patterned graphene nanocrosses for circularly polarized waves is achieved in the infrared regime. Broadband properties of anomalous refraction are demonstrated by investigating different frequencies and incident angles. Moreover, the anomalous conversion efficiency can be dynamically tuned and remain as high in a broadband frequency range by varying the Fermi energy without reoptimizing the nanostructures. This work may offer a further step in the development of a tunable wavefront controlling device.