Focusing of light by random scattering

TL;DR

This paper demonstrates that despite the diffusive nature of light in opaque media, it is possible to focus light sharply by controlling the wavefront, achieving a focus much brighter than the diffuse background.

Contribution

The authors show that wavefront shaping can focus light through opaque scattering media, with a universal relation explaining the results.

Findings

Achieved a focus 1000 times brighter than diffuse light

Demonstrated wavefront control in opaque materials like eggshells and paint

Quantitative explanation via statistical optics

Abstract

Random scattering of light is what makes materials such as white paint, clouds and biological tissue opaque. We show that although light propagating in these media is diffuse, a high degree of control is possible as phase information is not irreversibly lost. Opaque objects such as eggshell or white paint focus coherent light as sharply as a lens when illuminated with a wavefront that inverts the wave diffusion. We demonstrate the construction of such wavefronts using feedback, achieving a focus that is 1000 times brighter than the diffusely transmitted light. Our results are explained quantitatively by a universal relation based on statistical optics.