An achiral magnetic photonic antenna as a tunable nanosource of superchiral light

TL;DR

This paper proposes a tunable, achiral plasmonic nanoantenna that generates pure superchiral light with externally controllable chirality, enhancing sensitivity in molecular chirality detection at the nanoscale.

Contribution

It introduces a novel achiral magnetic plasmonic resonator capable of producing background-free, tunable superchiral light for improved chiral molecule detection.

Findings

Achieves background-free superchiral light generation.

Chirality sign is tunable via wavelength and polarization.

Potential for single-molecule sensitivity in circular dichroism.

Abstract

Sensitivity to molecular chirality is crucial for many fields, from biology and chemistry to the pharmaceutical industry. By generating superchiral light, nanophotonics has brought innovative solutions to reduce the detection volume and increase sensitivity at the cost of a non-selectivity of light chirality or a strong contribution to the background. Here, we theoretically propose an achiral plasmonic resonator, based on a rectangular nanoslit in a thin gold layer behaving as a magnetic dipole, to generate a tunable nanosource of purely superchiral light. This nanosource is free of any background, and the sign of its chirality is externally tunable in wavelength and polarization. These properties result from the coupling between the incident wave and the magnetic dipolar character of our nano-antenna. Thus, our results propose a platform with deep subwavelength detection volumes for chiral molecules in particular, in the visible, and a roadmap for optimizing the signal-to-noise ratios in circular dichroism measurements to reach single-molecule sensitivity.