Simulation of terahertz tunable seven-band perfect absorber based on high frequency detection function of Dirac semi-metallic nanowires

In this work, a tunable perfect absorber in the terahertz range is designed based on Dirac semimetal nanowires, featuring high sensitivity, quality factor, and dual functionality. The absorber achieves perfect absorptions across seven bands in a range of 0–14.5 THz: <i>f</i><sub>1</sub> = 5.032 THz (84.43%), <i>f</i><sub>2</sub> = 5.859 THz (96.23%), <i>f</i><sub>3</sub> = 7.674 THz (91.36%), <i>f</i><sub>4</sub> = 9.654 THz (99.02%), <i>f</i><sub>5</sub> = 11.656 THz (93.84%), <i>f</i><sub>6</sub> = 12.514 THz (98.47%), and <i>f</i><sub>7</sub> = 14.01 THz (97.32%). To ensure structural stability during design, the periodicity of the wire array structure is carefully considered. Verification of the absorber’s performance is conducted through the calculation of impedance matching. The analyses of the surface electric field and magnetic field at resonance frequency elucidate the underlying physical mechanisms governing the absorber’s characteristics. The values of quality factor (<i>Q</i>) for the seven resonance points are computed, with a maximum <i>Q</i> of 219.41. Further investigations by changing the external refractive index show that the maximum sensitivity value and the figure of merit (FOM) value are 5421.43 GHz/RIU and 35.204 RIU<sup>–1</sup>, respectively. Then, by discussing the influence of key parameters on the device, we conclude that the device can achieve the choice of dual fixed performance. Dynamic modulation capabilities are demonstrated by changing the Dirac semimetal’s Fermi energy. Additionally, by changing the incident angle of the external electromagnetic wave, it is found that the device has good stability in the medium frequency band and low frequency band, but it is greatly affected by the external incident angle in the high frequency band, thus necessitating careful consideration in practical applications. In conclusion, the proposed absorber holds significant promise for imaging, sensing, and detection applications, providing the valuable insights for designing optoelectronic devices.