Near-perfect multi-band graphene absorber with a compound grating-based resonant structure

We proposed a multi-band graphene absorber composed of a resonant compound grating (RCG), monolayer graphene, a thin silver layer, and a distributed Bragg reflector (DBR). A multi-band near-perfect absorption spectrum can be determined by three different physical mechanisms, including guided mode resonance (GMR), quasi-bound states in the continuum (quasi-BIC), and Tamm plasmon polaritons states (TPPs). Interestingly, the quasi-BIC mode can be achieved by changing grating layer spacing. In addition, the BIC mode can also be realized by varying grating periods. The variation of the absorption peak can be observed by changing the spacing layer thickness of the DBR structure, and the waveguide layer and grating layer thickness of the compound grating. Simulation results show that the absorption peaks of the three modes excited by our proposed absorbers are high as 80% at an incident light angle of 25°.