# Blind focusing through strongly scattering media using wavefront shaping with nonlinear feedback

## TL;DR

This paper demonstrates that wavefront shaping with nonlinear feedback enables blind focusing through strongly scattering media, supported by a validated model that predicts the process and minimal requirements for successful focusing.

## Contribution

The authors develop and experimentally validate a model describing blind focusing via nonlinear feedback, revealing conditions for effective wavefront shaping without localized feedback.

## Key findings

- Nonlinear feedback can enable blind focusing in turbid media.
- Maximizing nonlinear feedback does not always produce a focus.
- The model predicts minimal conditions for successful focusing.

## Abstract

Scattering prevents light from being focused in turbid media. The effect of scattering can be negated through wavefront shaping techniques when a localized form of feedback is available. Even in the absence of such a localized reporter, wavefront shaping can blindly form a single diffraction-limited focus when the feedback response is nonlinear. We developed and experimentally validated a model that accurately describes the statistics of this blind focusing process. We show that maximizing the nonlinear feedback signal does not always result in the formation of a focus. Using our model, we can calculate the minimal requirements to blindly focus light through strongly scattering media.