Observation of Photonic Chiral Flatbands

TL;DR

This paper reports the development of a nonlocal metasurface exhibiting strong, angle-independent chiral responses with high circular dichroism, enabling advancements in valley-selective optical devices and augmented reality.

Contribution

The study introduces a nonlocal metasurface with tunable, wide-angle chiral responses, surpassing previous narrow-angle limitations in chiral photonic devices.

Findings

Circular dichroism larger than 0.6 over ±5° incident angles

Resonant frequency and quality factor are tunable by design

Potential applications in valley-selective cavities and augmented reality

Abstract

Distinct selectivity to the spin angular momenta of photons have garnered significant attention in recent years, for their relevance in basic science and for imaging and sensing applications. While nonlocal metasurfaces with strong chiral responses to the incident light have been reported, these responses are typically limited to a narrow range of incident angles. In this study, we demonstrate a nonlocal metasurface that showcases strong chirality, characterized by circular dichroism larger than 0.6, over a wide range of incident angles $\pm5^o$. Its quality factor, circular dichroism and resonant frequency can be optimized by design. These findings pave the way to further advance the development of valley-selective optical cavities and augmented reality applications.