Mechanical separation of chiral dipoles by chiral light

TL;DR

This paper explores how chiral light exerts forces and torques on chiral dipoles, revealing mechanisms for enantiomeric separation based on optical chirality, with potential applications in chiral object sorting.

Contribution

It introduces a general framework for calculating chiral optical forces and links them to observable effects like optical rotation and circular dichroism, enabling mechanical separation of enantiomers.

Findings

Chiral forces depend on optical chirality density and flow.

Reactive and dissipative force components relate to optical rotation and circular dichroism.

Chiral forces enable potential enantiomeric separation strategies.

Abstract

We calculate optical forces and torques exerted on a chiral dipole by chiral light fields and reveal genuinely chiral forces in combining the chiral contents of both light field and dipolar matter. Here, the optical chirality is characterized in a general way through the definition of optical chirality density and chirality flow. We show in particular that both terms have mechanical effects associated respectively with reactive and dissipative components of the chiral forces. Remarkably, these chiral force components are directly related to standard observables: optical rotation for the reactive component and circular dichroism for the dissipative one. As a consequence, the resulting forces and torques are dependent on the enantiomeric form of the chiral dipole. This suggests promising strategies for using chiral light forces to mechanically separate chiral objects according to their enantiomeric form.