Institute for Theoretical Physics, Vienna University of Technology (TU Wien), Vienna, Austria.
Université de Rennes, CNRS, IETR (Institut d'Électronique et des Technologies du numéRique), UMR-6164, Rennes, France.
Nature. 2022 Jul;607(7918):281-286. doi: 10.1038/s41586-022-04843-6. Epub 2022 Jul 13.
The scattering of waves when they propagate through disordered media is an important limitation for a range of applications, including telecommunications, biomedical imaging, seismology and material engineering. Wavefront shaping techniques can reduce the effect of wave scattering, even in opaque media, by engineering specific modes-termed open transmission eigenchannels-through which waves are funnelled across a disordered medium without any back reflection. However, with such channels being very scarce, one cannot use them to render an opaque sample perfectly transmitting for any incident light field. Here we show that a randomly disordered medium becomes translucent to all incoming light waves when placing a tailored complementary medium in front of it. To this end, the reflection matrices of the two media surfaces facing each other need to 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 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.
当波在无序介质中传播时会发生散射，这对一系列应用来说是一个重要的限制，包括电信、生物医学成像、地震学和材料工程。波前整形技术可以通过工程特定的模式——称为开放传输本征通道——来减少波散射的影响，即使在不透明的介质中也是如此，这些模式可以引导波在无序介质中传播而不会发生任何后向反射。然而，由于这样的通道非常稀缺，因此不能使用它们来使不透明的样品对任何入射光场都完全透明。在这里，我们展示了当在随机无序介质前面放置一个定制的互补介质时，它会对所有入射光波变得半透明。为此，相互面对的两个介质表面的反射矩阵需要满足临界耦合条件的矩阵推广。我们通过数值和实验两种方法来实现这一方案，用于设计具有几十种散射元件的电磁波导。我们引入的这种半透明散射介质还具有一个很有前途的特性，即能够在其内部长时间存储入射辐射。
