Modelling of optical traps for aerosols

TL;DR

This paper develops a modified optical trapping model incorporating spherical aberration to better understand aerosol trapping, revealing that aerosol traps differ significantly from traditional optical tweezers and depend on particle and beam parameters.

Contribution

The paper introduces a modified Mie Debye spherical aberration model for aerosols, improving the understanding of optical trapping in stratified media.

Findings

Spherical aberration is essential for accurate aerosol trapping modeling.

Aerosol traps do not behave as true optical tweezers, showing variable trapping behavior.

The model qualitatively explains observed aerosol trapping phenomena.

Abstract

Experimental observations suggest that there are differences between the behavior of particles optically trapped in air and trapped in a liquid phase. We present a modified version of Mie Debye Spherical Aberration theory to numerically simulate such optical system in attempt to explain and predict these effects. The model incorporates Mie scattering and focussing of the trapping beam through media of stratified refractive index. Our results show a geometrical optics approach cannot correctly describe our system and that spherical aberration must be included. We successfully qualitatively explain the observed phenomena and those of other authors, before discussing the limits of our experimental techniques and methods to improve it. We draw the important conclusion that when optically trapping aerosols the system does not behave as a true `optical tweezers', varying between levitation and single beam gradient force trapping depending on particle and beam parameters.