Customized anti-reflection structure for perfect transmission through complex media

TL;DR

This paper introduces a method to make complex, disordered media fully transparent to all incident wavefronts by using a customized complementary structure, enabling perfect transmission and long-term radiation storage.

Contribution

It presents a novel approach to achieve complete wave transmission through complex media by designing a complementary structure satisfying a matrix critical coupling condition.

Findings

Numerical and experimental validation of the method.

Achieved perfect transmission through complex media.

Ability to store incident radiation for extended periods.

Abstract

Getting to grips with the detrimental influence of disordered environments on wave propagation is an interdisciplinary endeavour spanning diverse research areas ranging from telecommunications \cite{basar_wireless_2019} and bio-medical imaging \cite{kubby_wavefront_2019} to seismology \cite{Campillo2003} and material engineering \cite{Chen2010,Molesky2018}. Wavefront shaping techniques are highly promising to overcome the effect of wave scattering as even opaque media feature open channels for which the incident light is fully transmitted \cite{Dorokhov1984,Gerardin2014,Sarma2016,Jeong18}. With this feature being restricted, however, to just a small subset of judiciously engineered states it remains out of reach to render an opaque sample translucent for any incident light field. Here we show that a structureless medium composed of randomly assembled scattering elements can be made fully transmitting to all incoming wavefronts by putting a customized complementary medium in front of it. This special situation is achieved when the reflection matrices of the two media surfaces facing each other satisfy a matrix generalization of the condition for critical coupling. We implement this protocol both numerically and experimentally for the design of electromagnetic waveguides with several dozen scattering elements placed inside of them. The translucent scattering media we introduce here also have the promising property of being able to store incident radiation in their interior for remarkably long times.