Controlling the intensity of light in large areas at the interfaces of a scattering medium

TL;DR

This paper investigates how wavefront shaping can control and enhance light intensity across large areas at the interfaces of scattering media, revealing energy redistribution and long-range correlations.

Contribution

It experimentally demonstrates the dependence of intensity enhancement on the optimization area and uncovers energy redistribution and reflection-transmission correlations.

Findings

Enhancement increases with larger optimization radius.

Total reflected intensity decreases as transmitted intensity increases.

Evidence of long-range reflection-transmission correlation.

Abstract

The recent advent of wave-shaping methods has demonstrated the focusing of light through and inside even the most strongly scattering materials. Typically in wavefront shaping, light is focused in an area with the size of one speckle spot. It has been shown that the intensity is not only increased in the target speckle spot, but also in an area outside the optimized speckle spot. Consequently, the total transmission is enhanced, even though only the intensity in a single speckle spot is controlled. Here, we experimentally study how the intensity enhancement on both interfaces of a scattering medium depends on the optimization area on the transmission side. We observe that as the optimization radius increases, the enhancement of the total transmitted intensity increases. We find a concomitant decrease of the total reflected intensity, which implies an energy redistribution between transmission and reflection channels. In addition, we find a qualitative evidence of a long-range reflection-transmission correlation. Our result is useful for efficient light harvesting in solar cells, multi-channel quantum secure communications, imaging, and complex beam delivery through a scattering medium.