Spin Decoupling Metasurfaces for Four-Channel Terahertz Wavefront Shaping

Advances in wireless communication systems require multifunction-integrated optical devices to increase information capacities. However, the wavefront-shaping metasurfaces thus far face challenges in manipulating orthogonal polarization independently and achieving versatile wavefront shaping simultaneously. Here, the scheme of chip-integrated multi-section metalens geometries is proposed to operate simultaneously with efficient focusing, orthogonal polarization manipulation, and vortex beam generation. Two spin decoupling metasurfaces are prepared to implement four-channel terahertz wavefront shaping. It can independently engineer the co-polarized and cross-polarized components conversion under circularly polarized incidence. One metasurface realizes the polarization conversion in four independent channels under either left- or right-handed circular incidence. The other achieves different spin-to-orbit conversions to generate vortex beams with independent polarization manipulation in four channels. The results suggest promising applications for high-capacity and high-security terahertz communication.