Time-reversed magnetically controlled perturbation (TRMCP) optical focusing inside scattering media

TL;DR

This paper introduces a novel method for deep optical focusing inside scattering media using a magnetically controlled microsphere as an internal guidestar, enabling dynamic and targeted light manipulation for biomedical applications.

Contribution

The study presents a new approach combining magnetic control and digital optical phase conjugation to achieve sharp, dynamic optical focusing within scattering media.

Findings

Successful demonstration of sharp optical focusing through scattering media.

Enabling dynamic focusing with a large field-of-view via magnetic control.

Potential applications in targeted drug delivery and tumor imaging.

Abstract

Manipulating and focusing light deep inside biological tissue and tissue-like complex media has been desired for long yet considered challenging. One feasible strategy is through optical wavefront engineering, where the optical scattering-induced phase distortions are time reversed or pre-compensated so that photons travel along different optical paths interfere constructively at the targeted position within a scattering medium. To define the targeted position, an internal guidestar is needed to guide or provide a feedback for wavefront engineering. It could be injected or embedded probes such as fluorescence or nonlinear microspheres, ultrasonic modulation, as well as absorption perturbation. Here we propose to use a magnetically controlled optical absorbing microsphere as the internal guidestar. Using a digital optical phase conjugation system, we obtained sharp optical focusing within scattering media through time-reversing the scattered light perturbed by the magnetic microshpere. Since the object is magnetically controlled, dynamic optical focusing is allowed with a relatively large field-of-view by scanning the magnetic field externally. Moreover, the magnetic microsphere can be packaged with an organic membrane, using biological or chemical means to serve as a carrier. Therefore the technique may find particular applications for enhanced targeted drug delivery, and imaging and photoablation of angiogenic vessels in tumours.