Optical binding mechanisms: a conceptual model for Gaussian beam traps

TL;DR

This paper develops a conceptual model for optical binding in Gaussian beam traps, translating complex Mie scattering results into an intuitive understanding of particle interactions and arrangements.

Contribution

It introduces a physical description of optical binding mechanisms that explains particle behavior and trends, simplifying complex models into accessible insights.

Findings

Predicts non-uniform particle spacing in chains

Explains how particle number affects spacing

Provides an intuitive understanding of binding mechanisms

Abstract

Optical binding interactions between laser-trapped spherical microparticles are familiar in a wide range of trapping configurations. Recently it has been demonstrated that these experiments can be accurately modeled using Mie scattering or coupled dipole models. This can help confirm the physical phenomena underlying the inter-particle interactions, but does not necessarily develop a conceptual understanding of the effects that can lead to future predictions. Here we interpret results from a Mie scattering model to obtain a physical description which predict the behavior and trends for chains of trapped particles in Gaussian beam traps. In particular, it describes the non-uniform particle spacing and how it changes with the number of particles. We go further than simply \emph{demonstrating} agreement, by showing that the mechanisms ``hidden'' within a mathematically and computationally demanding Mie scattering description can be explained in easily-understood terms.