Programmable Chiral Radiation via Spin-Decoupled Metasurface with Integrated Compound Phases.

Chiral radiation holds promise for applications in sensing, communications, and information processing. Recent advances in optical materials and metasurfaces have enabled unprecedented control over their spectral and momentum characteristics. However, the dynamic reconfigurability of high-purity chiral radiation remains challenging due to the static architectures and intrinsic spin coupling which degrades polarization purity. Here, a programmable spin-decoupled metasurface is presented that integrates propagation and geometric phase at deeply subwavelength scales, enabling the generation of high-purity chiral beams with reconfigurable emission direction. By leveraging chiral radiators with a compound phase-decoupling strategy, directional control of the desired spin is achieved, whereas the unwanted component is suppressed through circular dichroism-based amplitude discrimination and phase modulation-induced destructive interference. Furthermore, the incorporation of positive intrinsic negative (PIN) diodes into the radiators enables active phase modulation, allowing real-time control over radiation direction. To validate the concept, a 1-bit programmable chiral metasurface is designed and fabricated with an overall thickness of 0.1λ0. Measurements confirm that the metasurface realizes chiral radiation over a wide angular range of ±45°, while maintaining high purity, as evidenced by a 3 dB axial ratio (AR) bandwidth of 10.4%. The proposed approach provides a compact and scalable solution for chirality and directionality engineering.