Investigation On Phase Manipulation Based On Active Metasurfaces With Phase-change Materials GSST

Metasurfaces have attracted widespread attention in the past two decades due to their unique ability to control the amplitude,phase,and polarization of electromagnetic waves.However,most metasurfaces based on traditional materials are limited by a single physical property and cannot be efficiently applied to multifunctional device design.Phase-change materials are special materials that can switch between different physical properties by electrical,optical,or thermal stimulation.Metasurfaces based on phase-change materials can be applied to the design of efficient multifunctional devices by changing the physical properties of the phase-change materials.While the tunable metasurfaces based on phase-change materials greatly enhance the ability to control electromagnetic waves by their controllable physical properties,reducing the difficulty of realizing multifunctional metasurfaces,the conjugate nature of the geometric phase of circularly polarized light still poses challenges for the reuse of circularly polarized light under different states on the same metasurface.And the ability of metasurfaces to control electromagnetic waves can be further improved by the multiplexing of circular-polarized light in different states and the independent regulation of left-circular-polarized(LCP)and right-circular-polarized(RCP)light in different states.Therefore,this article focuses on the research of the GSST-based metasurface,and combines the analysis and characteristics of the transmission phase and geometric phase to propose multifunctional switchable metasurfaces based on GSST,which achieves effective reuse and independent control of circularly polarized light under different phases on a single metasurface.The main research contents are as follows:(1)To address the difficulty of multiplexing circularly polarized light under different states,we combined the unique properties of geometric phase and transmission phase with the tunable optical characteristics of the phase-change material GSST,to achieve switching of photon spin-orbit interaction.The metasurface can obtain asymmetric photon spin-orbit interaction under crystalline state and symmetric photon spin-orbit interaction under amorphous state.Based on this principle,we designed a switchable metasurface for edge detection and focusing imaging,and its feasibility was verified by simulation.The metasurface was designed to achieve effective multiplexing of circularly polarized light under different states.The metasurface uses LCP and RCP light for edge detection under crystalline state,and LCP light for focusing imaging under amorphous state,and finally achieve efficient multiplexing of circularly polarized light under phase-change metasurface.(2)In response to the difficulty of independently controlling left-handed circularly polarized(LCP)and right-handed circularly polarized(RCP)light due to the correlation of geometric phase under different states,we introduce both transmission phase and geometric phase into tunable metasurfaces in amorphous and crystalline states.By decoupling the phase of the circularly polarized light with opposite polarization states under different states of the metasurfaces,we achieve independent control of LCP and RCP light under different states,thereby realizing multiple reuse of the metasurfaces.With this platform,a hyperlens with second-order focus switching and a vortex generator of topological charge with second-order switching are designed to verify its independent control effect.The results show that the platform successfully achieves independent control of LCP and RCP light under different states by decoupling the geometric phase under different states.