Transverse optical binding for a dual dipolar dielectric nanoparticle dimer

TL;DR

This paper provides analytical expressions for transverse optical binding forces and torques on dielectric dimers, revealing significant deviations from Rayleigh approximation predictions, especially for high-refractive-index particles, and highlighting the importance of magnetic interactions.

Contribution

It introduces an analytical model for optical forces and torques on dielectric dimers beyond Rayleigh approximation, emphasizing magnetic and hybridized dipolar interactions.

Findings

Magnetic interactions dominate the force for high-refractive-index particles.

Dimer stability is enhanced by one to four orders compared to Rayleigh predictions.

Torque increases by an order of magnitude due to coupling interactions.

Abstract

The physical origins of the transverse optical binding force and torque beyond the Rayleigh approximation have not been clearly expressed to date. Here, we present analytical expressions of the force and torque for a dual dipolar dielectric dimer illuminated by a plane wave propagating perpendicularly to the dimer axis. Using this analytical model, we explore the roles of the hybridized electric dipolar, magnetic dipolar, and electric-magnetic dipolar coupling interactions in the total force and torque on the particles. We find significant departures from the predictions of the Rayleigh approximation, particularly for high-refractive-index particles, where the force is dominated by the magnetic interaction. This results in an enhancement of the dimer stability by one to four orders of magnitude compared to the predictions of the Rayleigh approximation. For the case of torque, this is dominated by the coupling interaction and increases by an order of magnitude. Our results will help to guide future experimental work in optical binding of high-refractive-index dielectric particles.