Dual-functional reconfigurable metasurface for reversible circular and linear dichroism

Abstract

Dual-functional dichroic devices hold great potential applications in optical integrated systems, but most chiral devices are designed for a specific function of circular or linear dichroism (CD or LD). Herein, we numerically demonstrated a dichroic metasurface with giant and reversible CD and LD simultaneously by controlling the phase transition of Ge₂Sb₂Se₄Te₁(GSST) in a U-shaped array. By changing the symmetry of the structure via dynamically controlling the states of GSST inclusions, the maximum tuning ranges of CD of −0.89 to 0.89 and LD of −0.85 to 0.92 are achieved in the near-infrared (NIR) band. Theoretical analysis shows that the giant CD originates from the circular polarization selective excitations of magnetic dipole-electric quadrupole (MD-EQ) resonance, and the dual-band LD originates from the linear polarization selective excitations of MD-EQ and toroidal dipole (TD) resonances. To our knowledge, this is the first NIR metasurface capable of large-range switchable CD and LD simultaneously, which may provide new ideas for the design of polarization integrated devices.