Spin-dependent terahertz wavefront shaping based on hybrid phase in all-silicon chiral metasurfaces

Independent manipulation of orthogonal circularly polarized wavefronts is one of the important goals for meta-optics, and chiral nanophotonics is one of the crucial approaches. In this article, we propose a new scheme for spin-dependent terahertz wavefront shaping based on chiral metasurfaces, which involves a hybrid design of the propagation phase, chirality induced phase, and Pancharatnam-Berry phase in all-silicon meta-atoms. A controllable linear polarization conversion effect in the transmitted wave is obtained via breaking the mirror symmetry and preserving the C 2 symmetry of the resonator, which causes a different form of the Jones matrix. By simultaneously adjusting the in-plane geometric dimensions and azimuth angle of chiral units, and utilizing the evolution characteristics of circularly polarized components in parameter space and polarization space, spin-dependent phase responses have been observed. We provide the main theoretical analysis and demonstrate the functional design of circularly polarized multiplexed beam deflection or vortex beam generation, through the expected simulation and experimental results near the operating frequency of 0.6 THz. Our results may enrich the design of terahertz polarization-multiplexed devices.