Multi-band and high-sensitivity perfect absorber based on monolayer graphene metamaterial

Abstract The Finite Difference Time Domain (FDTD) method is used for the simulation, and a new method based on critical coupling and guided resonance is proposed theoretically and numerically to realize a multi-band ideal absorber (PA) of monolayer graphene. Its physical mechanism can be more perfectly analyzed through impedance matching and coupled mode theory (CMT). Due to the guided resonance (100% transmission or reflection efficiency is obtained through the coupling of the leakage mode and the guided mode under the phase matching condition), the perfect absorber can obtain four perfect absorption peaks. The resonance wavelengths are located at λ1 = 1085.03 nm, λ2 = 1131.48 nm, λ3 = 1187 nm and λ4 = 1365.35 nm, respectively. Their absorption rates are 95.88%, 99.81%, 97.44% and 95.30%. At the same time, we can also see a phenomenon in which the spectral position and value of the absorption peak can be adjusted by changing the relevant geometric parameters in the system (the geometric size, period, and incident angle of the hexagonal air hole absorber). Meanwhile, the structure we designed has certain advantages in the field of similar absorber research by briefly calculating related values of sensing performance. The sensitivity of its four resonance peaks are 46.45, 94.35, 151 and 598.9 nm/RIU, and FOM are 5.445, 11.192, 19.895 and 85.680. So we believe that the research has huge application prospects in terms of sensors, tunable spectrum detection, environmental monitoring and medical diagnosis, modulators and optoelectronic device sensors.