The device under study is shown in Fig. 1(a) and (b). The graphene
is placed on the top of the substrate whose bottom is deposited
with metal as a back reflector, and a dielectric layer is
sandwiched between the graphene and the metal grating. The
metal grating, dielectric spacer and graphene form a capacitor
where the grating and graphene serves as the two electrodes.
Hence, the Fermi energy of graphene can be dynamically tuned
by applying a voltage between the metal grating and the graphene.