A triple-functional integration terahertz device based on trapezoidal and stub resonators in bulk Dirac semimetals waveguide structure

This study introduces a BDS-insulator-BDS waveguide platform that simultaneously enables Fano resonance, band-stop filtering, and band-pass filtering at terahertz frequencies—a triple-functional integration achieved for the first time. Finite-difference time-domain (FDTD) simulations reveal that tuning geometric parameters, Fermi level, and relaxation time of the structure permits concurrent modulation of the band-stop filter bandwidth and spectral profile of the FR peaks. Notably, the plasmonic system exhibits exceptional environmental refractive index sensitivity, achieving a maximum sensitivity of 2.628 THz/RIU, with peak figure-of-merit (FOM) and quality factor (Q) values of 87.6 $RI{U}^{-1}$ and 154.88, respectively. This multi-parametric, multifunctional plasmonic module holds promise for advanced applications in terahertz slow-light systems, high-sensitivity sensing, tunable filtering, and miniaturized, highly integrated photonic devices.