Chiral discrimination by polarization singularities of a metal sphere

TL;DR

This paper introduces a novel method for chiral discrimination using polarization singularities in light scattering by a metal sphere, significantly enhancing detection sensitivity for small chiral particles.

Contribution

It demonstrates that polarization singularities can be exploited to improve chiral detection, surpassing traditional circularly polarized light methods, with potential applications in sensing and quantum optics.

Findings

Absorption dissymmetry is greatly enhanced on C lines compared to plane wave excitation.

The dissymmetry depends strongly on the anisotropy of the chiral particles.

The method can detect small helices with high sensitivity.

Abstract

The practical applications of chiral discrimination are usually limited by the weak chiral response of enantiomers and the high complexity of detection methods. Here, we propose to use the C lines (i.e., lines of polarization singularities) emerged in light scattering by a metal sphere to detect small chiral particles. Using full-wave numerical simulations and analytical multipole expansions, we determined the absorption dissymmetry of deep-subwavelength helices (i.e., chiral particles) at different positions on the C lines. We find that the absorption dissymmetry can be much larger than that induced by circularly polarized plane wave excitation, and it can be attributed to the asymmetric absorption of the induced electric and magnetic dipoles. We also show that the absorption dissymmetry strongly depends on the anisotropy of the helices. The results may find applications in optical manipulations, optical sensing, and chiral quantum optics.