A four-narrowband terahertz tunable absorber with perfect absorption and high sensitivity.

• According to COMSOL calculations, the absorption film has four perfect absorption peaks in the terahertz narrowband and exhibits polarization incoherence, which means that the absorption film has good performance. • By changing the physical parameters, the active tunability of the film in a wide range is achieved. • The absorption film has high refractive index sensitivity, which means it has extremely high application prospects. • With simple structures and materials, the phenomenon of absorption bandwidth of the absorber also facilitates the study of conversion and regulation between narrowband and broadband. Here, a simple four-band terahertz tunable narrowband absorber is proposed, which can achieve multimodal perfect absorption within 1–9 THz. We analyzed the physical mechanisms behind local surface plasmon resonance and impedance matching based on theoretical principles. By controlling the structural parameters, we use the eigen-mode and external field excitation to obtain the absorption peak and electromagnetic field distribution of the narrowband sensor under different structural parameters. Additionally, we studied the effect of the angle of incidence electromagnetic waves on the function of the absorber, found that the absorber has excellent characteristics in both low and high frequency states. We carry out a substance detection on four perfect absorption modes. The ambient refractive index sensitivity is 881.35 GHz / RIU , 439.65 GHz / RIU , 2664.46 GHz / RIU , 4501.19 GHz / RIU. The four-peak narrowband high-performance absorber designed by us has a huge development prospect in most important areas such as resource detection and biomedical diagnosis. [Display omitted] [ABSTRACT FROM AUTHOR]