Tunable circular dichroism in all-dielectric metasurface with efficient wavefront manipulation

In this paper, an all-dielectric metasurface based on phase-change material Ge2Sb2Se4Te1 (GSST) working in the mid-infrared band is designed, and combined with Pancharatnam-Berry (PB) phase to realize multifunctional metasurfaces. The metasurface can convert incident circularly polarized waves to transmitted or reflected waves of opposite chirality, regardless of GSST is in amorphous or crystalline state. Due to constructive interference and destructive interference, the metasurface obtains giant circular dichroism (CD). The maximum CD value reaches 0.997 at f = 64 THz when GSST is in amorphous state and 0.97 at f = 45 THz when GSST is in crystalline state. According to the principle of PB phase, three optical devices are realized by the rational arrangement of alldielectric meta-atoms with different rotation angles, which are beam deflectors, lenses and vortex beam generators.