Amplitude Modulation of Anomalously Refracted Terahertz Waves with Gated-Graphene Metasurfaces

Although recent progress in metasurfaces has shown great promise for applications, optical properties in metasurfaces are typically fixed by their structural geometry and dimensions. Here, an electrically controllable amplitude of anomalously-refracted waves in a hybrid graphene/metasurface system are experimentally demonstrated, which consists of an artificially constructed two-dimensional metallic apertures array and naturally occurring two-dimensional carbon atoms (graphene) in the subwavelength-scale (<lambda/10). Based on Pancharatnam-Berry phase and by careful design of a spatially linear phase profile, it is shown that the amplitude of anomalously refracted circularly cross-polarized terahertz waves can be effectively modulated by an applied gate voltage. The developed electrically tunable graphene metasurfaces may lead to various advanced applications that require dynamical control over electromagnetic waves, such as amplitude tunable active focusing lenses, vortex phase plates and dynamic holography.