Broadband terahertz absorber based on Dirac semimetal with tunable working bandwidth

A broadband metamaterial absorber (MA) based on bulk Dirac semimetal (BDS) with the property that the working bandwidth can be tuned is proposed. By changing the pattern on the top layer, the working band is expanded from narrowband to broadband. Interestingly, the working band over 90% absorption can be continuously changed from 0 to 3.4 terahertz (THz) when the Fermi energy level (EF) varies from 10 to 80 meV. The absorption mechanism of this broadband and tunable absorber is demonstrated and verified by the impedance matching theory, electric field, and power loss density distributions. Moreover, the proposed absorber is robust to the incident angle θ from 0°to 50°. Due to the symmetry structure, the designed absorber achieved the excellent property of polarization insensitivity. This proposed tunable broadband absorber may have a potential application in THz imaging and optoelectronic devices.