Giant Faraday Rotation in Graphene Metamolecules due to Plasmonic Coupling

We designed and numerically investigated a mechanism to enhance the polarization rotation when THz radiation passes through an array of multilayered graphene/insulator disks placed in a static magnetic field. The observed giant Faraday rotation is due to plasmonic coupling in the disks leading to the enhanced dipole oscillation strength of plasmonic antibonding states. With additional electromagnetic coupling between the disks in the array, the Faraday rotation angles nearly 30° are achieved in a relatively small external magnetic field of around 1 T. The operation wavelength can be tuned within the THz spectral range by controlling the Fermi level of graphene, number of graphene layers, and disk size and period. The proposed mechanism opens up a way to design the ultrathin magneto-optical nanophotonic devices and polarization rotators with high transmittance in the mid-infrared range.