Single-layered phase-change metasurfaces achieving efficient wavefront manipulation and reversible chiral transmission

Realization of a photoswitchable anapole metasurface based on phase change material Ge2Sb2Te5

The electromagnetic anapole mode originates from the phase cancellation interference between the far-field radiation of an oscillating electric dipole moment and toroidal dipole moment, which presents a radiation-free state of light while enhancing the near-field, and has potential applications in micro- and nanophotonics. The active control of the anapole is crucial for the design and realization of tunable photonic devices. In this paper, we realize dynamic tuning of an anapole metasurface and metasurface optical switching based on the phase change material G e 2 S b 2 T e 5 (GST). By utilizing the destructive interference of the electric dipole moment and ring dipole moment, we design the non-radiative anapole mode. At the same time, we introduce the phase change material GST to dynamically regulate the intensity and position of the far-field scattering, electric field, and transmission spectra, and to realize the transition from anapole mode to electric dipole mode. At the same time, the modulation of the transmission spectrum by the metasurface after the addition of GST film is achieved. A relative transmission modulation of 640.62% is achieved. Our study provides ideas for realizing effective active modulation of active micro- and nanophotonic devices, and promotes active modulation of active micro- and nanophotonic devices in lasers and filters and potential applications in dynamic near-field imaging.

Mid-infrared reconfigurable all-dielectric metasurface based on Ge2Sb2Se4Te1 phase-change material

In this paper, a reconfigurable all-dielectric metasurface based on Ge₂Sb₂Se₄Te₁ (GSST) phase-change material is proposed. By changing GSST from amorphous state to crystalline state, the metasurface can achieve high circular dichroism (CD) and wideband polarization conversion for circularly polarized waves in the mid-infrared (MIR) band. The maximum CD value reaches 0.95 at 74 THz, and circular polarization conversion efficiency is more than 90% in the wideband range of 41 THz - 48 THz. In addition, based on Pancharatnam-Berry phase, three kinds of wavefront manipulation of light have been realized: abnormal refraction, orbital angular momentum vortex beam and orbital angular momentum vortex beam splitting. This work has potential applications in the future MIR optical integrated system.