Fig. 1. Structure of fourfold symmetrical polarization-insensitive terahertz absorber

Fig. 2. Structure of the tunable terahertz absorber based on photosensitive silicon

Fig. 3. Structure of the tunable terahertz absorber based on silicon and germanium

Fig. 4. Absorptivity of fourfold symmetrical polarization-insensitive terahertz absorber

Fig. 5. Current distribution of fourfold symmetrical polarization-insensitive terahertz absorber. (a) Bottom current distribution of TE mode; (b) top current distribution of TE mode; (c) bottom current distribution of TM mode; (d) top current distribution of TM mode

Fig. 6. Relationship between the resonance frequency of the terahertz absorber and lateral length of the top metal

Fig. 7. Influence of polarization angle on absorption performance in different modes. (a) TE mode; (b) TM mode

Fig. 8. Absorption spectrum of the absorber under different conductivity conditions

Fig. 9. Rrelationship between the absorption performance of the terahertz absorber and semiconductor conductivity