# Programmable Chiral Radiation via Spin‐Decoupled Metasurface with Integrated Compound Phases

## TL;DR

A new metasurface design enables high-purity chiral radiation with adjustable emission direction using spin-decoupled structures and active phase control.

## Contribution

A programmable spin-decoupled metasurface is introduced for reconfigurable high-purity chiral radiation through compound phase integration and active modulation.

## Key findings

- A 1-bit programmable metasurface achieves ±45° scanning with 10.4% 3 dB axial ratio bandwidth.
- Spin-selective radiators and compound phase decoupling suppress unwanted polarization components.
- PIN diodes enable real-time directional control of chiral radiation.

## Abstract

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.

A programmable spin‐decoupled metasurface integrating propagation and geometric phases enables high‐purity chiral radiation with reconfigurable emission direction. Spin‐selective radiators combined with a compound phase decoupling strategy suppress undesired components, while embedded PIN diodes allow real‐time directional control. A 1‐bit prototype demonstrates ±45° scanning with 10.4% 3 dB axial ratio bandwidth, offering a compact platform for chirality engineering.