Single-shot Digital Optical Fluorescence Phase Conjugation Through Forward Multiply Scattering Samples

TL;DR

This paper introduces a novel single-shot, reference-free digital fluorescence phase conjugation technique that enables focusing light through complex scattering media using broadband speckle measurements from fluorescent beads.

Contribution

It presents a new method for wavefront measurement and focusing in scattering media without a reference beam, leveraging broadband speckle fields from fluorescent sources.

Findings

Successful focusing through scattering samples using single-shot measurement

Effective wavefront correction for broadband fluorescent signals

Demonstration of focusing at excitation wavelength in biological-like tissues

Abstract

Aberrations and multiple scattering in biological tissues critically distort light beams into highly complex speckle patterns. In this regard, digital optical phase conjugation (DOPC) is a promising technique enabling in-depth focusing. However, DOPC becomes challenging when using fluorescent guide-stars for four main reasons: The low photon budget available, the large spectral bandwidth of the fluorescent signal, the Stokes shift between the emission and the excitation wavelength, and the absence of reference beam preventing holographic measurement. Here, we demonstrate the possibility to focus a laser beam through multiple-scattering samples by measuring speckle fields in a single acquisition step with a reference-free, high-resolution wavefront sensor. By taking advantage of the large spectral bandwidth of forward multiply scattering samples, Digital Fluorescence Phase Conjugation (DFPC) is achieved to focus a laser beam at the excitation wavelength while measuring the broadband speckle field arising from a micron-sized fluorescent bead.