Visual guide to optical tweezers

TL;DR

This paper uses full field finite difference time domain simulations to visually explain the operation of optical tweezers across different particle sizes and scenarios, enhancing understanding beyond traditional approximations.

Contribution

It introduces a comprehensive visualization approach for optical tweezers using full field simulations, addressing limitations of geometric optics and Rayleigh approximations.

Findings

Full field simulations provide detailed insights into optical trapping mechanisms.

Visualizations help understand complex scenarios like engineered particles and evanescent fields.

Advances in computational methods enable better modeling of intermediate and large particles.

Abstract

It is common to introduce optical tweezers using either geometric optics for large particles or the Rayleigh approximation for very small particles. These approaches are successful at conveying the key ideas behind optical tweezers in their respective regimes. However, they are insufficient for modelling particles of intermediate size and large particles with small features. For this, a full field approach provides greater insight into the mechanisms involved in trapping. The advances in computational capability over the last decade has led to better modelling and understanding of optical tweezers. Problems that were previously difficult to model computationally can now be solved using a variety of methods on modern systems. These advances in computational power allow for full field solutions to be visualised, leading to increased understanding of the fields and behaviour in various scenarios. In this paper we describe the operation of optical tweezers using full field simulations calculated using the finite difference time domain method. We use these simulations to visually illustrate various situations relevant to optical tweezers, from the basic operation of optical tweezers, to engineered particles and evanescent fields.