All-silicon terahertz dielectric metasurface with polarization and phase decoupling modulation

Abstract All-dielectric chiral metasurfaces, as an emerging micro-nano optics device, have been favored in the fields of encrypted communication and optical device integration in recent years due to the strong circular dichroism and spinning effect at tiny sizes. Here, an all-silicon monolayer metasurface capable of simultaneous polarization and phase modulation is constructed. This approach transcends conventional limitations of single meta-atom wave manipulation by employing two pairs of chiral isomers to construct functional ‘meta-molecules’. Within each meta-molecule, the rotation of individual chiral meta-atoms imparts distinct phases to the excited circularly polarized light, which recombines into linearly polarized light with varied polarization in the transmitted wave. Subsequently, geometric phase modulation is incorporated between adjacent meta-molecules to achieve precise wavefront phase control. Through spectral analysis of simulations and theoretical calculations, this metasurface maintains 92% polarization conversion efficiency while accomplishing planar wavefront shaping. This metasurface, fabricated entirely from silicon, features high refractive index, low loss, and low cost, enabling direct processing with commercial silicon wafers. It establishes a novel platform for multi-parameter metasurface operations, demonstrating significant application value in THz imaging, sensing, and wireless communications.