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Focusing of light by random scattering

I. M. Vellekoop, A. P. Mosk

cond-mat.dis-nnarXiv:cond-mat/0604253

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.

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