Universal Quasi-Static Limit for Plasmon-Enhanced Optical Chirality

TL;DR

This paper shows that plasmonic nanostructures cannot significantly enhance optical chirality beyond plane wave levels due to fundamental electromagnetic constraints.

Contribution

It establishes a universal limit on optical chirality enhancement near plasmonic nanostructures, based on their quasi-static electromagnetic fields.

Findings

Average optical chirality near nanostructures is not significantly higher than plane waves.

The quasi-static nature of fields limits chirality enhancement.

Magnetic response at optical frequencies is too weak to boost chirality.

Abstract

We discuss the possibility of enhancing the chiroptical response from molecules uniformly distributed around nanostructures that sustain localized plasmon resonances. We demonstrate that the average optical chirality in the near field of any plasmonic nanostrucure cannot be significantly higher than that in a plane wave. This conclusion stems from the quasi-static nature of the nanoparticle-enhanced electromagnetic fields and from the fact that, at optical frequencies, the magnetic response of matter is much weaker than the electric one.