Fig. 1. Schematic of the first absorber. (a) 5×5 array; (b) top view and (c) side view of unit structure

Fig. 2. Absorptivity of decomposition structure of the first absorber. (a) Square ring with outer-protrusions; (b) square ring with inner-protrusions; (c) two combined square rings; (d) two square rings connected by gold blocks

Fig. 3. Absorption curves and surface current distributions of the first absorber under different GaAs conductivities. (a) Dynamic absorption curves; surface current distributions at (b) 0.53 THz, (c) 1.32 THz, and (d) 0.686 THz

Fig. 4. Schematic of tunable multi-state absorber. (a) Top view and (b) side view of unit structure

Fig. 5. Absorption curves of the second absorber under different conditions. (a1) No pump light,σ_GaAs=100 S·m^-1;(a2) 1550 nm pump light,σ_GaAs=1×10³ S·m^-1; (a3) 1550 nm pump light, σ_GaAs=2×10³ S·m^-1; (a4) 1550 nm pump light,σ_GaAs=5×10³ S·m^-1; (a5) 1550 nm pump light,σ_GaAs=1×10⁴ S·m^-1; (a6) 1550 nm pump light,σ

Fig. 6. Surface current distributions of the second absorber under different conditions. (a) No pump light, 0.518 THz; (b) no pump light, 0.906 THz;(c) no pump light, 1.514 THz; (d) 1500 nm pump light, 0.524 THz; (e) 1500 nm pump light, 1.106 THz; (f) 800 nm pump light, 0.706 THz

Fig. 7. Absorptivity of the second absorber versus polarization angle and incidence angle under different absorption modes. (a1)(b1)(c1) Triple-band absorption; (a2)(b2)(c2) dual-band absorption; (a3)(b3)(c3) single-band absorption