Enrichment of deeply penetrating waves in disordered media

TL;DR

This paper introduces an iterative wavefront control method to selectively couple incident waves to high-transmission eigenmodes in disordered media, significantly enhancing deep wave penetration for optical imaging and therapy.

Contribution

The authors develop a novel iterative wavefront control technique to enrich high-transmission eigenmodes, overcoming previous challenges in complex disordered media.

Findings

Achieved over 3-fold increase in light transmission through scattering media

Method is effective with only reflected wave detection, suitable for in vivo use

Enhances optical imaging depth and therapeutic applications

Abstract

Waves incident to a highly scattering medium are incapable of penetrating deep into the medium due to the diffusion process induced by multiple scattering. This poses a fundamental limitation to optically imaging, sensing, and manipulating targets embedded in opaque scattering layers such as biological tissues. One strategy for mitigating the shallow wave penetration is to exploit eigenmodes with anomalously high transmittance existing in any disordered medium. When waves are coupled to these eigenmodes, strong constructive wave interference enhances deeply penetrating waves. However, finding such eigenmodes has been a challenging task due to the complexity of disordered media. In this Letter, we present an iterative wavefront control method that selectively enriches the coupling of incident beam to high-transmission eigenmodes. Specifically, we refined the high-transmission eigenmodes from an arbitrary initial wave by either maximizing transmitted wave intensity or minimizing reflected wave intensity. Using the proposed method, we achieved more than a factor of 3 increases in light transmission through a scattering medium exhibiting hundreds of scattering events. Our approach is readily applicable to in vivo applications in which only the detection of reflected waves is available. Enhancing light penetration will lead to improving the working depth of optical imaging and treatment techniques.