Unambiguous definition of handedness for locally-chiral light

TL;DR

This paper introduces a clear and precise definition of handedness for locally-chiral light fields, enabling better characterization and application of these complex polarization states in nonlinear chiral interactions.

Contribution

It provides the first unambiguous definition of handedness for locally-chiral light, addressing a key gap in understanding their chiral properties.

Findings

Defined a new measure of handedness for locally-chiral light

Enabled practical calculations of light's chirality sign

Facilitated improved analysis of chiral light-matter interactions

Abstract

Synthetic chiral light fields were recently introduced as a novel source of chirality [Ayuso et al. Nat. Phot. 13, 866 (2019)]. This locally-chiral light spans a three-dimensional polarization that plots a chiral trajectory in space-time, leading to huge nonlinear chiral signals upon interactions with chiral media. The degree of chirality of this new form of light was defined, characterized, and shown to be proportional to the chiral signal conversion efficiency. However, the sign of the light's chirality - its 'handedness' - has not yet been defined. Standard definitions of helicity are inapplicable for locally-chiral light due to its complex three-dimensional structure. Here, we define an unambiguous handedness for locally-chiral fields and employ it in practical calculations.