Lateral Chirality-sorting Optical Spin Forces in Evanescent Fields

TL;DR

This paper explores how evanescent fields produce lateral optical forces on chiral particles, enabling potential passive chirality sorting and spectroscopy with forces stronger than previously predicted.

Contribution

It introduces a novel mechanism where evanescent fields generate lateral forces dependent on particle chirality, surpassing earlier force predictions.

Findings

Lateral optical forces depend on particle chirality.

Forces can be used for passive chirality sorting.

Force strength exceeds previous predictions.

Abstract

The transverse component of the spin angular momentum of evanescent waves gives rise to lateral optical forces on chiral particles, which have the unusual property of acting in a direction in which there is neither a field gradient nor wave propagation. As their direction and strength depends on the chiral polarizability of the particle, they act as chirality-sorting and may offer a mechanism for passive chirality spectroscopy. The absolute strength of the forces also substantially exceeds that of other recently predicted sideways optical forces, such that they may more readily offer an experimental confirmation of the phenomenon.