Graphene-based dual-band near-perfect absorption in Rabi splitting between topological edge and Fabry–Perot cavity modes

Abstract

We propose a graphene embedded one-dimensional (1D) topological photonic crystal heterostructure, where the coupling occurs between the topological edge mode (TEM) and the Fabry–Perot cavity mode (CM). It is shown that the coupling leads to the hybridization between TEM and CM, with a Rabi splitting. Based on finite element method, a dual-band near-perfect absorption is found in the Rabi splitting region in near-infrared range. The resonant wavelengths of the two absorption peaks are 1537 and 1579 nm, respectively. And the two absorption peaks can be modulated by the thickness of the defect layer, the coupling distance between TEM and CM, Fermi energy of graphene, and incident angle of light (under TE and TM polarization). In particular, when the Fermi energy of graphene slightly increases over 0.4 eV, the imaginary part of permittivity of graphene is near 0, so does the dual-band absorption. Theoretically, the TEM-CM coupling can be analyzed by the classic oscillator model. The controllable two absorption bands may achieve potential applications in active optoelectronic devices at communication wavelengths, such as optical switches, sensors and modulators.