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

Area of Science:

• Metasurfaces and Nanophotonics
• Chiral Optics
• Electromagnetics

Background:

• Chiral radiation is crucial for advanced applications like sensing and communications.
• Current metasurfaces struggle with dynamic reconfigurability and maintaining polarization purity due to static designs and spin coupling.
• Achieving controllable, high-purity chiral beams is a significant challenge in optical engineering.

Purpose of the Study:

• To present a novel programmable spin-decoupled metasurface for generating high-purity chiral radiation.
• To enable dynamic and reconfigurable control over the emission direction of chiral beams.
• To overcome the limitations of static metasurface architectures in chiral radiation applications.

Main Methods:

• Integration of propagation and geometric phase at subwavelength scales.
• Development of chiral radiators employing a compound phase-decoupling strategy.
• Incorporation of positive intrinsic negative (PIN) diodes for active phase modulation and real-time directional control.
• Utilizing circular dichroism-based amplitude discrimination and destructive interference for suppressing unwanted spin components.

Main Results:

• Demonstration of a 1-bit programmable chiral metasurface with a thickness of 0.1λ₀.
• Realization of chiral radiation with reconfigurable emission direction over a wide angular range (±45°).
• Maintenance of high purity in chiral beams, evidenced by a 3 dB axial ratio bandwidth of 10.4%.

Conclusions:

• The proposed metasurface offers a compact and scalable solution for engineering chirality and directionality.
• This work advances the dynamic control of chiral radiation, paving the way for next-generation optical devices.
• The spin-decoupled approach successfully addresses the challenge of polarization purity degradation in reconfigurable chiral metasurfaces.