Optical focusing inside scattering media with time-reversed ultrasound microbubble encoded (TRUME) light

TL;DR

TRUME is a novel optical focusing technique inside scattering media that uses microbubble destruction and wavefront measurement to achieve sub-ultrasound wavelength resolution and improve focus precision.

Contribution

The paper introduces TRUME, a new method that enhances optical focusing resolution in scattering media by leveraging microbubble destruction and wavefront shaping.

Findings

Achieves ~2 micron optical focus size.

Demonstrates 2-fold resolution improvement.

Breaks ultrasound focus resolution barrier.

Abstract

Focusing light inside scattering media in a freely addressable fashion is challenging, as the wavefront of the scattered light is highly disordered. Recently developed ultrasound-guided wavefront shaping methods are addressing this challenge, albeit with relatively low modulation efficiency and resolution limitations. In this paper, we present a new technique, time-reversed ultrasound microbubble encoded (TRUME) optical focusing, which is able to focus light with improved efficiency and sub-ultrasound wavelength resolution. This method ultrasonically destructs microbubbles, and measures the wavefront change to compute and render a suitable time-reversed wavefront solution for focusing. We demonstrate that the TRUME technique can create an optical focus at the site of bubble destruction with a size of ~2 microns. Due to the nonlinear pressure-to-destruction response, the TRUME technique can break the addressable focus resolution barrier imposed by the ultrasound focus. We experimentally demonstrate a 2-fold addressable focus resolution improvement in a microbubble aggregate target.