Fig. 1. (a) x-y plane diagram of the periodic structure of the broadband absorber；(b) 3 D schematic diagram of the absorber, where P=104 μm, R₁=11 μm, R₂= 38 μm, R₃=26 μm, t_s =15 μm, t_m =2 μm

Fig. 2. Absorption spectra of the proposed absorber with various values of the graphene chemical potential μ from 0 to 0.9 eV

Fig. 3. The electric field distributions (|E|) of the proposed absorber on the x–y plane with z = 50 nm at the different graphene chemical potential μ of (a) 0.1, (b) 0.2 and (c) 0.4 eV

Fig. 4. (a) Simulated absorption spectra of the proposed G-SemiEllip/SemiSphere absorber (red line) and four other absorbers with NN (black line), G-SemiSphere (blue line), G-SemiEllip (green line) and N-SemiEllip/SemiSphere (pink line)

Fig. 5. The electric field distributions (|E|) of the proposed absorber on the x-y plane with z = 50 nm at the different frequencies of (a) 0.82 THz, and (b) 4.95 THz

Fig. 6. (a) The change rate of absorptivity with polarization angle (angle between electric field direction and y-axis) at oblique incident of TE wave; (b)-(c) The rate at which the absorptivity varies with the incidence angle θ (the angle between the incident direction and the z-axis) for oblique incidence of TE/TM waves