A five-band terahertz metamaterial absorber with properties of polarization-insensitive and wide-angle tolerance based on bulk Dirac semimetal

We design a bulk Dirac semimetal (BDS) metamaterial-based terahertz absorber consisted of a BDS layer, a dielectric layer and a gold grounding layer from top to bottom, which produces five excellent terahertz absorption peaks having 99.55%, 99.63%, 99.65%, 97.72%, and 99.87% absorption at 0.49 THz, 0.85 THz, 1.68 THz, 2.00 THz, and 2.27 THz, respectively. The five-band BDS-based absorber is polarization-insensitive and wide-angle tolerance, with good absorption in the incident angle range of 0 degrees-60 degrees. The tuning of the Fermi energy level of BDS in the range of 40-70 meV enables the dynamic adjustment of absorption frequencies and absorption rates of these peaks. We also analyze the refractive index sensing sensitivity of five-band BDS-based absorber, it is revealed that when the refractive index of surrounding analyte is changed from 1.0 to 1.8, the refractive indices of the five absorption peaks are 57.75 GHz/RIU, 107.25 GHz/RIU, 101.75 GHz/RIU, 101.75 GHz/RIU, and 134.75 GHz/RIU, which approximately exhibit an enhanced sensing sensitivity as the absorption frequency increases. The design is simultaneously characterized by multiple bands, high absorption, high stability,and high refractive index sensitivity, which should have great potential for application in the fields of terahertz technology.