Fig. 1. Schematic diagrams of absorber unit cell. (a) Side view of unit cell; (b) top view of unit cell; (c) schematic of applying voltage to graphene

Fig. 2. Conductivity of graphene at different Fermi levels. (a) Real part of conductivity; (b) imaginary part of conductivity

Fig. 3. Simulated absorption spectra of absorber under different VO₂ states

Fig. 4. Absorption spectra and relative impedance of absorbers under different VO₂ states. (a) Metallic state; (b) insulating state

Fig. 5. Distributions of surface current and magnetic field of YOZ plane. (a)(e)(i)(m) Current distributions of graphene at four frequency points; (b)(f)(j)(n) current distributions of VO₂ at four frequency points; (c)(g)(k)(o) current distributions of metal substrate of structure at four frequency points; (d)(h)(l)(p) magnetic field distributions of air above graphene structure at four frequency points

Fig. 6. Absorption spectra of absorber under different Fermi levels of graphene and different conductivity of VO₂. (a) Absorption spectra under different Fermi levels of graphene; (b) absorption spectra _{under different conductivities of VO2; (c) absorption spectra for varying both conductivity of VO2 and Fermi levels of graphene}

Fig. 7. Absorption spectra of absorber with different polarization angles

Fig. 8. Absorption spectra of absorber at different incident angles,and distributions of magnetic field on YOZ plane with different polarization modes and different incident angles at frequency of 0.99 THz. (a) Absorption spectrum for TE polarization; (b) absorption spectrum for TM polarization; (c) distributions of magnetic field on YOZ plane with different polarization modes and different incident angles at frequency of 0.99 THz

Fig. 9. Absorption characteristics for different refractive indices of object to be measured and absorber sensitivity; (a) Absorption characteristics for different refractive indices of object to be measured; (b) absorber sensitivity

Table 1. Absorption characteristics of absorber under different Fermi levels

Table 2. Performance comparison between different absorbers