Noninvasive nonlinear imaging through strongly-scattering turbid layers

TL;DR

This paper introduces a noninvasive method for achieving diffraction-limited imaging through strongly scattering media by leveraging optical nonlinearities, enabling high-resolution microscopy without invasive feedback.

Contribution

It presents a novel nonlinear wavefront-shaping technique that forms a focus inside scattering media without localized feedback, supported by theoretical, numerical, and experimental validation.

Findings

Successful formation of diffraction-limited focus inside scattering samples

Demonstration of two-photon microscopy through opaque layers

Noninvasive imaging achieved without invasive feedback signals

Abstract

Diffraction-limited imaging through complex scattering media is a long sought after goal with important applications in biomedical research. In recent years, high resolution wavefront-shaping has emerged as a powerful approach to generate a sharp focus through highly scattering, visually opaque samples. However, it requires a localized feedback signal from the target point of interest, which necessitates an invasive procedure in all-optical techniques. Here, we show that by exploiting optical nonlinearities, a diffraction-limited focus can be formed inside or through a complex sample, even when the feedback signal is not localized. We prove our approach theoretically and numerically, and experimentally demonstrate it with a two-photon fluorescence signal through highly scattering biological samples. We use the formed focus to perform two-photon microscopy through highly scattering, visually opaque layers.