Fig. 1. Schematic diagram of the proposed metadevice and the experimental setup. (a) The functional diagram of the LC-integrated cascaded metadevice with 6 spin-dependent vortex channels. (b) The detailed structure of the metadevice; Micrographs of (c) dielectric metasurface and (d) plasmonic metasurface. (e) Schematic diagram of N/F-STS system, in which the measurement methods of NF and FF are illustrated.

Fig. 2. Structure scheme of the single plasmonic metasurface layer and its performances. (a) Simulated and experimental anisotropic transmission spectrum of metal slit array with a=160 μm, b=50 μm. (b) Schematic diagram of the plasmonic metasurface, the right part is the detailed diagrams of paired slits and the k^th spiral-arrayed slit pair resonator. (c) The function of a single plasmonic metasurface layer. (d) Simulated and (e) experimental NF/FF intensity and phase distributions at f₀=0.475 THz.

Fig. 3. Structure scheme of the single dielectric metasurface and its performance results. (a) Schematic diagram of spin-decoupled all-dielectric metasurface containing pillars with 5 geometric sizes. Inset: perspective and top views of meta-atoms. (b) The simulated anisotropic phase delays, (c) phase shifts, and (d) transmission coefficients in the x direction under 45°-LP incidence when the width w and the length q are swept from 60 μm to 280 μm. The selected rectangle pillars are marked with dots. (e) The simulated and experimental FF intensity and phase distribution.

Fig. 4. Results and evaluations of designed cascaded metadevice. (a) The simulated and (b) experimental intensity and phase distribution of 12-mode vortices at the central frequency f₀. (c) The vortex mode purity matrix and (d) isolation of 6 channels in simulation when the LC orientation is along the y- and z-axis.

Fig. 5. Illustrations of the active modulation in the 2 NF channels. With the LC orientation rotating in the y-z plane, (a) the simulated evolution process of the intensity and phase distributions of PVs with P = zL and zR at the frequency f₀. (b) the measured evolution process of intensity distributions. (c) The dynamic modulation process of the mode purity for PVs in simulation. (d) Simulated and experimental modulation ratio of the expected PV modes.

Fig. 6. Illustrations of the active modulation in the 4 FF channels. With the LC orientation rotating in the y-z plane, the (a) simulated and (b) measured evolution process of the intensity distributions at the frequency f₀. (c) The dynamic modulation process of the mode purity for FVs in simulation. (d) Simulated and experimental modulation ratio of the expected FV modes.