Directional Scattering-Induced Optical Forces on a Mie Particle near a Metal Interface

TL;DR

This paper investigates how directional scattering influences optical forces on dielectric nanoparticles near a metal interface, revealing mechanisms for optical sorting based on scattering-induced forces.

Contribution

It demonstrates the link between scattering directionality and optical forces, enabling control and sorting of resonant nanoparticles near metal surfaces.

Findings

Interference of dipole moments causes highly directional scattering into free-space and SPP channels.

Optical forces can be tuned over a 2π range by adjusting scattering directionality.

Optical sorting of nanoparticles is feasible by exploiting scattering-induced force variations.

Abstract

Optical manipulation of Mie-resonant dielectric nanoparticles is strongly influenced by their enhanced scattering and multipolar response, which fundamentally modifiesthe balance of optical forces. In this work, we study the optical forces acting on a resonant dielectric nanoparticle placed near a metal interface, where scattering occurs into both free-space and surface plasmon-polariton (SPP) channels. We show that the interference of electric and magnetic dipole moments leads to highly directional scattering in these channels, and the direction and magnitude of the scattering-induced force are directly linked to the angular directivity of the corresponding radiation channels. We show that in a cross-beam configuration, where the radiation-pressure contribution is suppressed, the optical force can be changed for almost 2{\pi} in a wide range of particle sizes that provides a route toward optical sorting of resonant nanoparticles.