Dynamically tunable Fano resonance in planar structures based on periodically asymmetric graphene nanodisk pair

We present a dynamically frequency tunable Fano resonance planar device composed of periodically asymmetric graphene nanodisk pair for the mid-infrared region. The two asymmetric graphene nanodisks can be directly excited by the light simultaneously and produce two kinds of reflected light with almost the same spectrum linewidth. By studying the local field distributions of our structure, we find that there are two kinds of modes for the two asymmetric graphene nanodisks, i.e., the symmetric mode and antisymmetric mode. Resonance coupling between the symmetric and antisymmetric modes generates the Fano resonance in our structure. This Fano resonance generation mechanism is different from it in traditional Fano resonance structure. In the traditional Fano resonance structure, the Fano resonance comes from the coupling effect between continuum and discrete structure. Moreover, we find that both of the Fano resonance amplitude and frequency of the structure can be dynamically controlled by varying the Fermi energy of graphene. Resonance transition in the structure is studied to reveal the physical mechanism behind it.