Fluorescence-based optical phase conjugation through scattering media

Project Information

FLUO.OPC

Grant agreement ID: 101105899

DOI

10.3030/101105899

Project closed

EC signature date 29 June 2023

Start date 1 September 2023

End date 31 August 2025

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 195 914,88

Coordinated by

SORBONNE UNIVERSITE
France

Periodic Reporting for period 1 - FLUO.OPC (Fluorescence-based optical phase conjugation through scattering media)

Reporting period: 2023-09-01 to 2025-08-31

Summary of the context and overall objectives of the project

The ability to generate and control light through complex media such as thick biological tissue is essential for optical microscopy and many biomedical applications. However, strong scattering within such media severely limits our capacity to manipulate light. Recent advances in wavefront shaping have made progress in addressing this challenge, but these methods rely on coherent laser light and thus cannot be applied to fluorescence, which underpins modern microscopy techniques.
Expanding the ability to focus or deliver light to multiple or extended fluorescent targets would greatly broaden the range of applications, particularly in deep-tissue optogenetics, where fluorescent probes enable precise and targeted labeling.
This project aims to achieve active control of light propagation through scattering media by exploiting fluorescence signals from fluorescent objects. By combining advanced holographic techniques to extract information from fluorescence with optical phase conjugation, the project seeks to demonstrate that light can be accurately focused through thick, highly scattering media guided by fluorescence.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

This project developed a computational method to retrieve optical fields from scattered fluorescence signals and demonstrated its application for refocusing light and imaging fluorescent objects hidden behind scattering media. A custom microscope system was designed and built, incorporating a spatial light modulator to control fluorescence, integrated with a high-sensitivity sCMOS camera to capture fluorescence signals under strong scattering conditions. In addition, a computational algorithm was developed to model the experimental configuration and iteratively reconstruct multiple optical field information within the fluorescence signal. These combined developments enabled the demonstration of high-precision light focusing through scattering media, achieving accurate positioning and high contrast at obscured fluorescent object positions. The work further established a method to analyze the retrieved optical field information to separate contributions from individual fluorescent sources. Building on this capability, three-dimensional volumetric imaging of fluorescent objects was successfully demonstrated under strong scattering conditions.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

This project demonstrated light shaping and fluorescence imaging of targets under scattering conditions where conventional approaches fall short. The scattering strength was sufficient to overwhelm traditional adaptive optics methods, which cannot adequately correct such severe light distortions that extend beyond simple aberration models. The developed method uniquely retrieves the complete scattered optical field information, including both amplitude and phase components. This capability enables extraction of three-dimensional positional information for precise light control targeting and volumetric imaging of fluorescent objects through scattering media. Such information is fundamentally inaccessible with conventional microscopy techniques that can only measure light intensity or capture distorted images of objects, lacking access to the crucial wavefront (phase) information of light. The demonstrated capability to perform multi-target light control and three-dimensional imaging through strong scattering opens significant opportunities for deep tissue biological imaging, where light scattering has traditionally imposed fundamental limits on achievable imaging depth and resolution.