Graphene-based terahertz metamirror with wavefront reconfiguration

As an emerging material, graphene has been widely applied in the field of active metasurface. Recently, researchers employed graphene to achieve dynamical control of electromagnetic wavefront. In this work, graphene-based reflective metasurface is presented to realize dynamical wavefront reconfiguration for terahertz wave. Using a hybrid structure of cross-shaped graphene and metal patch, the designed metasurface has 360° phase modulation capability. Its wavefront is reconfigurable and can realize multiple functions. In order to verify this, three examples are designed to demonstrate the phenomenon of wavefront reconstruction. They are gradient metasurface, vortex beam generator, and focusing mirror, respectively. First of all, Fermi level of graphene is used to reconstruct the reflected wavefront of gradient metasurface, and then realize switching between positive and negative reflections. Secondly, a vortex beam generator is implemented, and it can reconstruct the mode number of orbital angular momentum through Fermi level. Finally, a reflective lens is proposed and verified, whose focus can appear or disappear with the tuning of Fermi level. The proposed functions have potential applications in the fields of terahertz switching, communication, and focusing.