A “belfry-typed” narrow-band tunable perfect absorber based on graphene and the application potential research

In this work, the overall structure of the proposed “belfry-typed” absorber sensor is composed of four layers, from bottom to top are Si substrate, Au layer, SiO2 dielectric layer and the top “belfry-typed” graphene layer, respectively. Among them, the design of the “bell tower” pattern is inspired by the common bell tower building in daily life. Compared with the previous absorber based on frequency superposition method, the patterned graphene structure greatly simplifies the actual processing steps. By using FDTD to simulation, it is found that the structure has two perfect resonance absorption modes with absorption rates of 99.92% and 99.88% at 7578 nm and 8635 nm. Considering that the special surface plasmon tunability of graphene, the two-mode regulation can be achieved by controlling Fermi energy, relaxation times and structural geometry parameters. Moreover, the refractive index sensitivity of the device was discussed. The three basic parameters evaluating the performance of sensor are 1477.5 nm/RIU of sensitivity, 25.47 of FOM and 123.4 of quality factor. Finally, the specific circumstance of the absorber applied in actual life such as in aqueous solution, 10%, 20%, 25%, 60% glucose solution and 30%, 50% sugar solution was simulated and discussed. These results suggest that the proposed absorber has high refractive index sensitivity and high response speed, with which the absorber has high application value in photoelectric detection, switching and imaging.