Focusing large spectral bandwidths through scattering media

TL;DR

This paper demonstrates methods to significantly increase the spectral bandwidth for wavefront shaping through scattering media, enabling improved multispectral nonlinear imaging in biological tissues.

Contribution

It introduces techniques to access and enlarge the spectral memory in scattering media by minimizing axial spatio-spectral coupling and using broadband excitation.

Findings

Spectral bandwidth involves axial spatio-spectral coupling.

Confocal geometry minimizes spectral decorrelation.

Broadband excitation further enlarges spectral bandwidth.

Abstract

Wavefront shaping is a powerful method to refocus light through a scattering medium. Its application to large spectral bandwidths or multiple wavelengths refocusing for nonlinear bio-imaging in-depth is however limited by spectral decorrelations. In this work, we demonstrate ways to access a large spectral memory of a refocus in thin scattering media and thick forward-scattering biological tissues. First, we show that the accessible spectral bandwidth through a scattering medium involves an axial spatio-spectral coupling, which can be minimized when working in a confocal geometry. Second, we show that this bandwidth can be further enlarged when working in a broadband excitation regime. These results open important prospects for multispectral nonlinear imaging through scattering media.