Fig. 1. Chiral metasurface absorber based on twisted catenary structure. (a) The schematic image of the proposed metasurface. LCP incidence will be totally absorbed by the metasurface, while the RCP incidence will be largely reflected; (b) The 3D (top) and top view (bottom) schematic images of the unit cell

Fig. 2. The comparison between the traditional catenary structure and the twisted catenary structure. (a) The schematic image of traditional catenary structure; (b) The reflected amplitude and (c) absorption under different circularly polarized incidence; (d) The schematic image of twisted catenary structure; (e) The reflected amplitude and (f) absorption under different circularly polarized incidence

Fig. 3. The absorption performance under different incident angles. (a)~(c) φ=0°, θ=0~60°, (a) A_LCP，(b) A_RCP and (c) ∆A; (d)~(f) φ=90°, θ=0~60°, (d) A_LCP，(e) A_RCP and (f) ∆A

Fig. 4. The physical mechanism for the chiral absorption of the twisted catenary structure. (a) The normalized electric field distribution under different circularly polarized incidence at the working wavelength; (b) The normalized electric field distribution under different circularly polarized incidence at the non- working wavelength; (c) The reflected amplitude under linearly polarized incidence; (d) The reflected phase under linearly polarized incidence

Fig. 5. The information encryption verification based on the twisted catenary structures. (a) The mirrored unit cell as that in Figure 2(d) and its absorption; (b) The original image for information encryption; The simulated near field image under LP (c), LCP (d) and RCP (e) incidence

Fig. 6. The information encryption application based on the twisted catenary structure. (a) The sample image for information encryption; The calculated near field image under (b) LP or unpolarized, (c) LCP and (d) RCP incidence