Controlling dispersion forces between small particles with artificially created random light fields

TL;DR

This paper demonstrates both theoretically and experimentally that artificially created random light fields can induce and control isotropic dispersion forces between small colloidal particles, offering new ways to manipulate colloidal interactions.

Contribution

It introduces a novel method to induce and control isotropic dispersion forces using artificially generated fluctuating light fields, contrasting with traditional anisotropic optical forces.

Findings

Experimental evidence of isotropic attractive interactions between dielectric microspheres

Demonstration of control over interaction strength and range in colloidal systems

Theoretical prediction confirmed by experimental results

Abstract

Appropriate combinations of laser beams can be used to trap and manipulate small particles with "optical tweezers" as well as to induce significant "optical binding" forces between particles. These interaction forces are usually strongly anisotropic depending on the interference landscape of the external fields. This is in contrast with the familiar isotropic, translationally invariant, van der Waals and, in general, Casimir-Lifshitz interactions between neutral bodies arising from random electromagnetic waves generated by equilibrium quantum and thermal fluctuations. Here we show, both theoretically and experimentally, that dispersion forces between small colloidal particles can also be induced and controlled using artificially created fluctuating light fields. Using optical tweezers as gauge, we present experimental evidence for the predicted isotropic attractive interactions between dielectric microspheres induced by laser-generated, random light fields. These light induced interactions open a path towards the control of translationally invariant interactions with tuneable strength and range in colloidal systems.