Actively modulating near-infrared absorption of monolayer graphene in a compound grating-coupled waveguide structure

In this work, we numerically study the tunable light absorption of monolayer graphene at the near-infrared region by the guided mode resonance in a compound grating-coupled waveguide structure. A biased graphene capacitor is placed below the coupled waveguides. The electromagnetically induced transparency phenomenon is demonstrated by the resonant coupling of guided modes. The light absorption of monolayer graphene at the transparency window can be dynamically tuned by shifting the Fermi energy of graphene in capacitor. The absorption modulation depth of monolayer graphene at the transparency window can vary quickly from zero to nearly 100 % around the interband transition of graphene in capacitor. These results have potential applications in the active photodetectors and photoconductive devices.