Non-zero helicity extinction in light scattered from achiral (or chiral) small particles located at points of null incident helicity density

TL;DR

This paper reveals that helicity extinction can occur in light scattered from small particles at points of zero incident helicity density, due to interference effects, providing new insights beyond standard circular dichroism.

Contribution

It introduces a unified formulation showing helicity extinction enhancement through interference, applicable to achiral particles and revealing information on polarizabilities beyond CD.

Findings

Helicity extinction occurs even at zero incident helicity density.

Interference between circular components influences helicity extinction.

The phenomenon provides information on electric and magnetic polarizabilities.

Abstract

Based on a recent unified formulation on dichorism and extinction of helicity on scattering by a small particle, dipolar in the wide sense, magnetodielectric or not, chiral or achiral, we show that such extinction is enhanced not only at resonances of the polarizabilities, but also due to interference between left and right circularly polarized components of the incident wave, which contributes with appropriate parameters of the illuminating field, even if the particle is achiral and is placed at points of the incident field at which the local incident helicity density is zero. This phenomenon goes beyond standard circular dichroism (CD), and we analyze it in detail on account of the values of the several quantities, both of the incident light and the particle, involved in the process. In addition, this interference produces a term in the helicity extinction that remarkably yields information on the real parts of the electric and/or magnetic polarizabilities, which are not provided by CD, of which that helicity extinction phenomenon may be considered a generalization.