Fig. 1. Schematic diagram of the designed extrinsic chiral metasurface structure array and its unit cell structure. (a) The principle of extrinsic chirality and the direction of oblique incidence; (b) Unit cell structure; (c) The specific structural parameters

Fig. 2. (a) Dielectric constants of amorphous and crystalline GST ^[27-28]; (b) Sketch of phase transitions between crystalline and amorphous phases of GST^[8]

Fig. 3. Transmission coefficients for (a) crystalline and (b) amorphous states of GST

Fig. 4. The CD spectra for amorphous and crystalline states of GST at θ = 50° and φ = 0°

Fig. 5. The curve of CD parameters with different incidence angles θ in GST (a) amorphous and (b) crystalline states when φ = 0°; The curve of CD parameters with different incidence projection angles φ in GST (c) amorphous and (d) crystalline states when θ = 50°

Fig. 6. The CD spectra with different (a) period p and (b) thickness t in the amorphous state of GST layer

Fig. 7. Electric field distribution when θ = 0°，φ = 0°. (a) Crystalline GST, LCP incidence, f =130 THz; (b) Crystalline GST, RCP incidence, f =130 THz; (c) Amorphous GST, LCP incidence, f = 200 THz; (d) Amorphous GST, RCP incidence, f = 200 THz

Fig. 8. Electric field distribution when θ = 50°，φ = 0°. (a) Crystalline GST, LCP incidence, f =130 THz; (b) Crystalline GST, RCP incidence, f =130 THz; (c) Amorphous GST, LCP incidence, f = 200 THz; (d) Amorphous GST, RCP incidence, f = 200 THz