Phase conjugation with spatially incoherent light in complex media

TL;DR

This paper introduces a phase conjugation technique for spatially incoherent light that enables non-invasive, targeted light focusing inside complex scattering media, advancing control over light propagation in biological tissues.

Contribution

The authors develop a novel phase conjugation method for incoherent light that allows focusing on multiple targets without physical access, using speckle pattern analysis and digital time-reversal.

Findings

Successfully focus light on multiple targets inside scattering media.

Achieve maximum energy delivery to extended targets.

Demonstrate control of light propagation using incoherent emission.

Abstract

Shaping light deep inside complex media, such as biological tissue, is critical to many research fields. Although the coherent control of scattered light via wavefront shaping has made significant advances in addressing this challenge, controlling light over extended or multiple targets without physical access inside a medium remains elusive. Here we present a phase conjugation method for spatially incoherent light, which enables the non-invasive light control based on incoherent emission from multiple target positions. Our method characterizes the scattering responses of hidden sources by retrieving mutually incoherent scattered fields from speckle patterns. By time-reversing scattered fluorescence with digital phase conjugation, we experimentally demonstrate focusing of light on individual and multiple targets. We also demonstrate maximum energy delivery to an extended target through a scattering medium by exploiting transmission eigenchannels. This paves the way to control light propagation in complex media using incoherent contrasts mechanisms.