A variety of adjustable terahertz absorbers based on bulk Dirac semi-metal

Abstract This paper presents the design of a terahertz absorber based on Dirac semimetals, capable of achieving triple-band narrowband absorption in the 6–10 THz range. The absorber integrates a protective alumina dielectric layer on top of the conventional ‘sandwich’ structure, providing enhanced durability. The center frequencies of the three absorption peaks are located at 7.16 THz, 8.5 THz, and 9.615 THz, with corresponding absorption rates of 97.33%, 98.03%, and 93.80%. The quality factors (Q) of the three peaks are 40.89, 162.84, and 125.20, respectively. The underlying mechanisms of this triple-band absorption are explored through impedance matching theory and surface plasmon resonance theory. Furthermore, by leveraging the tunable Fermi level of the Dirac semimetal, dynamic tuning of the absorber is demonstrated. Owing to the rotational symmetry of the structure, the absorber exhibits robustness in complex electromagnetic environments. Additionally, refractive index sensitivity studies reveal a strong linear correlation between the central frequencies of the absorption peaks and the surrounding refractive index. The highest sensitivity achieved is 1854.6 GHz/RIU. Within the refractive index range of 1.0–1.2, the figure of merit (FOM) reaches a maximum of 29.68, indicating that the absorber maintains excellent narrowband characteristics while providing high sensitivity. In summary, the proposed absorber shows significant potential for further application in fields such as biomedical sensing and space exploration.