Colloidal suspensions in modulated light fields

TL;DR

This paper explores how modulated light fields influence phase transitions in dense colloidal suspensions, revealing effects on particle behavior and interactions, including the impact of particle size and radiation pressure.

Contribution

It demonstrates that modulated light fields can induce phase transitions in dense colloidal systems, extending previous work on dilute systems and analyzing technical and size-related effects.

Findings

Particles are strongly affected by modulated potentials in dense systems

Effects depend on modulation wavelength and radiation pressure

Particle size relative to wavelength influences system behavior

Abstract

Periodically-modulated potentials in the form of light fields have previously been applied to induce reversible phase transitions in dilute colloidal systems with long-range interactions. Here we investigate whether similar transitions can be induced in very dense systems, where inter-particle contacts are important. Using microscopy we show that particles in such systems are indeed strongly affected by modulated potentials. We discuss technical aspects relevant to generating the light-induced potentials and to imaging simultaneously the particles. We also consider what happens when the particle size is comparable with the modulation wavelength. The effects of selected modulation wavelengths as well as pure radiation pressure are illustrated.