Experimental creation and characterization of random potential energy landscapes exploiting speckle patterns

TL;DR

This paper experimentally creates and characterizes a tunable random potential energy landscape using speckle patterns, enabling control over the landscape's roughness and length scales for colloid manipulation.

Contribution

It introduces a novel optical setup that generates and characterizes tunable random potential energy landscapes with controllable statistical properties.

Findings

Speckle patterns and rPELs follow Gamma distributions.

Contrast and roughness are tunable via speckle standard deviation.

Diffuser rotation allows creation of flat potentials.

Abstract

The concept of potential energy landscapes is applied in many areas of science. We experimentally realize a random potential energy landscape (rPEL) to which colloids are exposed. This is achieved exploiting the interaction of matter with light. The optical set-up is based on a special diffuser, which creates a top-hat beam containing a speckle pattern. This is imposed on colloids. The effect of the speckle pattern on the colloids can be described by a rPEL. The speckle pattern as well as the rPEL are quantitatively characterized. The distributions of both, intensity and potential energy values, can be approximated by Gamma distributions. They can be tuned from exponential to approximately Gaussian with variable standard deviation, which determines the contrast of the speckles and the roughness of the rPEL. Moreover, the characteristic length scales, e.g. the speckle size, can be controlled. By rotating the diffuser, furthermore, a flat potential can be created and hence only radiation pressure exerted on the particles.