Free‐Standing Bilayer Metasurface With Physically Separated Phase Modulations for Low‐Crosstalk Polarization Multiplexing

Polarization multiplexing metasurfaces are promising for high‐capacity wavefront manipulation but typically suffer from inter‐channel crosstalk that degrades the fidelity of each polarization channel. This paper presents a free‐standing bilayer spin‐decoupled metasurfaces that achieves almost complete decoupling of two circular polarization channels by physically separating the geometric phase and propagation phase modulations into distinct layers. This design overcomes the parametric constraints of single‐layer metasurfaces and maintains high polarization conversion rate. As a demonstration, we implement a dual‐channel beam shaping metasurfaces. Compared with traditional single‐layer design, our device exhibits significant low crosstalk, with the crosstalk suppression ratio (CSR) of the two channels improved by 5.08 and 6.91 dB respectively, and the efficiency and uniformity have also been improved. The device also maintains low crosstalk operation over a wavelength range of ± 30 nm. In addition, dual‐channel hologram shows substantially improved clarity. This approach offers a robust route toward high‐fidelity polarization multiplexed meta‐devices.