Spontaneous natural optical activity in disordered media

TL;DR

This paper reveals that disordered media composed of non-chiral plasmonic resonators can exhibit natural optical activity due to their intrinsic geometric chirality, with the effect depending on scattering properties and confirmed by simulations.

Contribution

It demonstrates the emergence of natural optical activity in disordered, non-chiral media and links it to geometric chirality and scattering characteristics, using theoretical and simulation methods.

Findings

Optical activity depends on the scattering mean free path.

Disordered media exhibit statistical distributions of rotatory power.

Chirality in disordered systems can be quantified by standard deviation measures.

Abstract

We demonstrate natural optical activity in disordered ensembles of non-chiral plasmonic resonators. We show that the statistical distributions of rotatory power and spatial dichroism are strongly dependent on the scattering mean free path in diffusive random media. This result is explained in terms of the intrinsic geometric chirality of disordered media, as they lack mirror symmetry. We argue that chirality and natural optical activity of disordered systems can be quantified by the standard deviation of both rotatory power and spatial dichroism. Our results are based on microscopic electromagnetic wave transport theory coupled to vectorial Green's matrix method for pointlike scatterers, and are independently confirmed by full-wave simulations.