Probing the chirality of a single microsphere trapped by a focused vortex beam through their orbital period

TL;DR

This paper demonstrates a high-precision method to characterize the chirality of individual microspheres trapped by vortex beams, leveraging their orbital period dependence to improve enantioselective measurements significantly.

Contribution

It introduces a novel optical trapping technique that uses orbital period sensitivity to determine particle chirality with enhanced accuracy.

Findings

Orbital period depends strongly on particle chirality.

The method achieves at least ten times higher precision than existing approaches.

Effective for weak light-chiral matter interactions at the single-particle level.

Abstract

When microspheres are illuminated by tightly focused vortex beams, they can be trapped in a non-equilibrium steady state where they orbit around the optical axis. By using the Mie-Debye theory for optical tweezers, we demonstrate that the orbital period strongly depends on the particle's chirality index. Taking advantage of such sensitivity, we put forth a method to experimentally characterize with high precision the chiroptical response of individual optically trapped particles. The method allows for an enhanced precision at least one order of magnitude larger than that of similar existing enantioselective approaches. It is particularly suited to probe the chiroptical response of individual particles, for which light-chiral matter interactions are typically weak.