Metasurfaces with maximum chirality empowered by bound states in the continuum

TL;DR

This paper introduces chiral metasurfaces that leverage bound states in the continuum to achieve maximum optical chirality, enabling sharp resonances and enhanced circular dichroism for advanced photonic applications.

Contribution

It presents a novel design of chiral metasurfaces utilizing BICs to attain maximum chirality, validated through numerical simulations.

Findings

Achieved arbitrarily sharp resonances with maximum chirality.

Demonstrated narrow peaks in circular dichroism spectra.

Validated design through numerical simulations.

Abstract

We demonstrate that rotationally symmetric chiral metasurfaces can support arbitrarily sharp resonances with the maximum optical chirality determined by precise shaping of bound states in the continuum (BICs). Being uncoupled from one circular polarisation of light and resonantly coupled to its counterpart, a metasurface hosting the chiral BIC resonance exhibits a narrow peak in the circular dichroism spectrum. We propose a realization of such chiral BIC metasurfaces based on pairs of dielectric bars and validate the concept of maximum chirality by numerical simulations