Tunable Triple-Band Terahertz Absorber Based on Bulk-Dirac-Semimetal Metasurface

A tunable triple-band absorber based on bulk-Dirac-semimetal (BDS) metasurface is proposed in the terahertz (THz) range. The design is comprised of a BDS film with a pattern of dual ring slots and a dielectric layer stacked on a fully reflective gold ground. And the electric or magnetic resonances result in the incident plane waves at different frequencies to be effectively absorbed by the BDS film, which leads to the high absorption at 1.56 THz, 3.28 THz, and 3.95 THz resonant frequencies. The tunability of the resonant frequencies depends on various Fermi levels. Moreover, the physical mechanisms of the absorber with good stability over wide incident angles and polarization insensitivity are expounded. The proposed BDS-based absorber has great potentials in sensors, thermal emitters, and energy harvesting, etc.