Selective coupling of optical energy into the fundamental diffusion mode of a scattering medium

TL;DR

This paper demonstrates experimentally that wavefront shaping can selectively couple light into the fundamental diffusion mode within scattering media, enhancing energy density and with implications for various optical applications.

Contribution

The study introduces a model describing energy density distribution in scattering media using wavefront shaping, validated by experimental data without adjustable parameters.

Findings

Enhanced fluorescent power with optimized wavefronts

Energy density increases with sample thickness

Model accurately predicts energy distribution in scattering media

Abstract

We demonstrate experimentally that optical wavefront shaping selectively couples light into the fundamental diffusion mode of a scattering medium. The total energy density inside a scattering medium of zinc oxide (ZnO) nanoparticles was probed by measuring the emitted fluorescent power of spheres that were randomly positioned inside the medium. The fluorescent power of an optimized incident wave front is observed to be enhanced compared to a non-optimized incident front. The observed enhancement increases with sample thickness. Based on diffusion theory, we derive a model wherein the distribution of energy density of wavefront-shaped light is described by the fundamental diffusion mode. The agreement between our model and the data is striking not in the least since there are no adjustable parameters. Enhanced total energy density is crucial to increase the efficiency of white LEDs, solar cells, and of random lasers, as well as to realize controlled illumination in biomedical optics.