Circularly Polarized Multiplexed Terahertz Bessel Beams Generation Based on Chiral Metasurfaces Without C 2 Symmetry

The efficient generation of diffraction-free beams is of great significance for applications in terahertz communications and sensing. Metasurfaces, renowned for their powerful wavefront manipulation and planar integration advantages, present an ideal platform for this purpose. This paper proposes an all-silicon chiral metasurface that achieves efficient decoupling of the left- and right-handed circularly polarized (LCP/RCP) components by breaking the C2 rotational symmetry of its meta-atoms. Based on the equivalent axicon approach and by leveraging the principles of both chiral phase and geometric phase, the designed metasurface converts an incident terahertz plane wave into two spatially separable, zero-order Bessel-like beams, which exhibit remarkable diffraction-free propagation characteristics. Full-wave simulations and experimental measurements using a terahertz time-domain spectroscopic imaging system collectively verify this capability. This work thus provides an effective strategy for developing high-performance, easy-to-integrate multifunctional terahertz devices.