Terahertz absorbers with ultra-broadband and ultra-narrowband absorption capabilities are essential for built-in and environment friendly terahertz modulation. This paper proposes a dual-mode tunable terahertz absorber based mostly on the section transition traits of vanadium dioxide (VO2), enabling dynamic switching between narrowband and broadband absorption by means of its insulating-to-metallic transition. Within the insulating state, the excitation of quasi-bound states within the continuum (Q-BIC) resonance by way of geometric parameter modulation of silicon pillars is investigated, with its bodily mechanism elucidated by means of impedance matching principle and multipole evaluation. This mode demonstrates distinctive sensing efficiency at 8.017 THz: a refractive index sensitivity of three.735 THz/RIU, a top quality issue (Q) of 4800.89, and a determine of advantage (FOM) reaching 3822.93 RIU-1. When VOâ‚‚ is remodeled into the metallic state, the gadget achieves greater than 90% ultra-broadband absorption within the vary of three.93 THz to 9.25 THz, and its broadband absorption property originates from the electrical dipole resonance. As well as, the impact of fabric structural parameters on the broadband absorption efficiency was investigated, and it was discovered that the efficiency of the gadget remained secure when completely different structural parameters had been used. In comparison with current applied sciences, this design integrates twin functionalities in a single-layer hybrid construction, considerably lowering fabrication complexity. It gives novel insights for terahertz sensing, environment-adaptive gadgets, and multifunctional photonic chips.
