Asymmetric longitudinal optical binding force between two identical dielectric particles with electric and magnetic dipolar responses

TL;DR

This paper analytically demonstrates an unexpected asymmetric longitudinal optical binding force between two identical dielectric particles with electric and magnetic responses, revealing complex nonequilibrium dynamics and potential for light-driven assembly.

Contribution

It introduces the first analytical demonstration of asymmetric optical binding forces in identical dual dipolar particles under incoherent illumination.

Findings

Asymmetric force results from dipolar hybridization and coupling.

Force decays with the first power of interparticle distance.

Rich nonequilibrium dynamics observed in the particle pair.

Abstract

In general,the optical binding force between identical particles is thought to be symmetric.However,we demonstrate analytically a counter-intuitively asymmetric longitudinal optical binding force between two identical dual dipolar dielectric particles.This homodimer is confined in two counter-propagating incoherent plane waves along the dimer's axis.The force consists of the electric dipolar,magnetic dipolar,and electric-magnetic dipolar coupling interactions.The combined effect of these interactions is markedly different than the expected behavior in the Rayleigh approximation.The asymmetric force is a result of the asymmetric forward and backward scattering of the particles due to the dipolar hybridization and coupling interactions.Consequently,it leads to a harmonic driving force on the pair,which decays with the interparticle distance to the first power.We show the rich nonequilibrium dynamics of the dimer and of the two particles impelled by the driving and binding forces and discuss the ranges of particle refractive index and size in which the asymmetric binding force arises.Our results open perspectives for nonequilibrium light-driven multiparticle transport and self-assembly.