Fig. 1. Geometric structure of absorber. (a) Three-dimensional view of periodic unit cell; (b) top view of periodic unit cell; (c) side view of periodic unit cell

Fig. 2. Numerical results under different conductivities when electromagnetic wave is vertically incident. (a) Absorption spectra; (b) reflection spectra

Fig. 3. Absorptivity and relative impedance of absorber under different conditions. (a) (b) VO₂ at metal phase; (c) (d) VO₂ at insulation phase

Fig. 4. Electric field diagrams at different conductivities. （a） 100 S·m^-1； （b） 1000 S·m^-1； （c） 5000 S·m^-1； （d） 30000 S·m^-1

Fig. 5. Influence of opening size on absorber when absorptivity is 100 S·m^-1 and 30000 S·m^-1, respectively

Fig. 6. Absorption spectra under different conditions. (a) Different polarization angles; (b) TE wave, different incident angles; (c) TM wave, different incident angles