▎ 摘　　要

In this paper, we propose a tunable dual band perfect absorption structure based on cross four split ring resonator (CFSRR). The structure presented uses SiO2 as an isolation layer to separate the bottom silver layer from the top cross four split ring resonator, with which can capture more light energy and provide possibility to realizing perfect absorption. The finite difference time domain (FDTD) method is used to simulate the calculation, and some significant phenomena and conclusions are obtained. The simulation results show that the proposed structure can achieve dual band perfect absorption, and the performance of absorber can be tuned to any selected wavelength within the specified wavelength range by carefully designing the structural parameters (such as R, r, P, L, W, etc.) of the absorber. In addition, changing the Fermi level of graphene with the method of applying voltage gate can dynamically tunable the absorption performance of the structure without rebuilding a new structure. In this way, the manufactural cost is greatly saved. Finally, by changing the refractive index of the surrounding medium, the sensing performance of the structure is studied, and the sensing performance of the short wavelength and long wavelength can reach 20.48 mu m/RIU and 25.77 mu m/RIU, respectively. And the maximum value of FOM 4.55 and Q-factor reaches 10.84. This work has important reference value for the application of modulator, sensor and photoelectric device in practice.