Single- and dual-band convertible terahertz absorber based on bulk Dirac semimetal

Abstract

A single- and dual-band convertible perfect absorber based on bulk Dirac semimetal (BDS), in which BDS disk array embedded in a dielectric layer deposited on the metal substrate, is proposed. In the use of new materials, we integrate two different modes in a simple structure which not complicatedly patterns the structure of BDS. The simulated results show that the full width at half maximum (FWHM) of mode f1 and mode f2 are Δf=4×10−2 THz and 2.4 ×10−2 THz, respectively. And the absorption spectra of our absorber can be well described by the coupled mode theory (CMT). Comprehensive analyses show that, for dual-band absorber, the two absorption peaks can be attributed to the localized cavity resonance and the inter-cell electric resonance, separately. It is interesting to find that double-band absorber can be converted to single-band absorber when the radius of BDS disk is chosen appropriately. Unlike traditional metal-based absorber, absorption frequency of the proposed absorber can be adjusted by varying Fermi energy of BDS from 20 to 50 meV while maintaining high absorption efficiency over 92%. Moreover, the proposed absorber is robust to incident angles from 0°to 60°. Thus, this paper may provide a guideline to investigate single- and dual-band convertible absorber with simple structure based on BDS.