A broadband tunable THz sensor based on graphene metasurface

In this paper, we design a polarization-independent and angle-insensitive wideband THz graphene metamaterial sensor. The proposed metasurface sensor consists of six layers, which are silicon dioxide substrate, metal reflector, air layer, graphene metasurface with microstructure, ion-gel layer and silicon dioxide dielectric layer from bottom to top. The sensor was simulated by using CST Microwave Studio software, and the absorption and sensing performance were analyzed. The results show that the absorption rate is more than 95 % in the range of 1.05-4.07 THz. In addition, when the Fermi energy level of graphene is changed, the absorption rate can be adjusted from 20 % to more than 95 %. At the same time, the absorptivity of the device can be maintained above 80 % before 60 degrees when the TE and TM waves are incident, and it is insensitive to the polarization angle due to the central symmetry of the graphene surface microstructure. By changing the thickness of the air layer, the device can achieve maximum absorption at h2 = 30 mu m, where the maximum frequency shift sensitivity is 2.179 THz/ RIU. The influence of structure parameters and incident angle on the absorption spectrum shows that the proposed structure has good stability. The proposed metasurface sensor has potential application prospects in biological detection and medical monitoring, broadening the application range of THz functional devices.