Optimal Concentration of Light in Turbid Materials

TL;DR

This paper demonstrates that by shaping the wave front of light, it is possible to concentrate light energy into a spot smaller than a wavelength inside turbid materials, approaching the physical limit of focus size.

Contribution

It introduces a method to optimally concentrate light in turbid media, achieving near-physical-limit focusing through wave front shaping.

Findings

Achieved light concentration within 68% of the physical limit.

Enhanced intensity on a hidden dyed probe sphere.

Supported by comparison of emission and excitation light enhancements.

Abstract

In turbid materials it is impossible to concentrate light into a focus with conventional optics. Recently it has been shown that the intensity on a dyed probe inside a turbid material can be enhanced by spatially shaping the wave front of light before it enters a turbid medium. Here we show that this enhancement is due to concentration of light energy to a spot much smaller than a wavelength. We focus light on a dyed probe sphere that is hidden under an opaque layer. The light is optimally concentrated to a focus which does not exceed the smallest focal area physically possible by more than 68%. A comparison between the intensity enhancements of both the emission and excitation light supports the conclusion of optimal light concentration.