Tunable Fano resonance and optical switching in the one-dimensional topological photonic crystal with graphene

Abstract

A hybrid structure composed of a grating coupled graphene structure and two one-dimensional photonic crystals (PhCs) is investigated, where the topological edge state (TES) and the graphene surface plasmon polariton (GSPP) are coupled to generate Fano resonances. The grating coupled graphene structure is used to excite the GSPP and provides a broad resonance. The two PhCs are designed to possess opposite topological properties; thus, the TES appears at the interface and exhibits a narrow resonance. The constructive and destructive interference between the GSPP and the TES results in the Fano resonance. By analyzing the resonant behaviors, it is found that the line shape of Fano resonance can be actively tuned by the graphene Fermi energy. We apply our results to the optical switching, a high-performance optical switch is achieved, and the modulation depth can reach as high as 23.31 dB. In addition, owing to the characteristic of Fano resonance with steep dispersion and asymmetric profile, our designs might offer an alternative strategy to achieve potential applications in sensors, filters, optical switches, and slow-light devices.