Fast binarized time-reversed adapted-perturbation (b-TRAP) optical focusing inside scattering media

TL;DR

This paper introduces a rapid, high-gain, large-mode optical focusing method inside scattering media, enabling real-time deep tissue imaging and manipulation with unprecedented speed and efficiency.

Contribution

It presents a novel binarized time-reversal technique that achieves millisecond-scale focusing, surpassing previous methods in speed, gain, and mode capacity for in vivo applications.

Findings

Achieved real-time focusing in dynamic scattering media

Extended laser speckle contrast imaging to greater depths

Demonstrated millisecond-scale phase-conjugation

Abstract

Light scattering inhibits high-resolution optical imaging, manipulation and therapy deep inside biological tissue by preventing focusing. To form deep foci, wavefront-shaping and time-reversal techniques that break the optical diffusion limit have been developed. For in vivo applications, such focusing must provide high gain, high speed, and a large number of spatial modes. However, none of the previous techniques meet these requirements simultaneously. Here, we overcome this challenge by rapidly measuring the perturbed optical field within a single camera exposure followed by adaptively time-reversing the phase-binarized perturbation. Consequently, a phase-conjugated wavefront is synthesized within a millisecond, two orders of magnitude shorter than the digitally achieved record. We demonstrated real-time focusing in dynamic scattering media, and extended laser speckle contrast imaging to new depths. The unprecedented combination of fast response, high gain, and large mode count makes this work a major stride toward in vivo deep tissue optical imaging, manipulation, and therapy.