INSA Rennes, CNRS, IETR-UMR 6164, F-35000 Rennes, France.
Department of Applied Physics, Yale University, New Haven, CT 06520, USA.
Sci Adv. 2023 Jan 25;9(4):eadf0323. doi: 10.1126/sciadv.adf0323.
We demonstrate experimentally that reflectionless scattering modes (RSMs), a generalized version of coherent perfect absorption, can be functionalized to perform reflectionless programmable signal routing. We achieve versatile programmability both in terms of operating frequencies and routing functionality with negligible reflection upon in-coupling, which avoids unwanted signal power echoes in radio frequency or photonic networks. We report in situ observations of routing functionalities like wavelength demultiplexing, including cases where multichannel excitation requires adapted coherent input wavefronts. All experiments are performed in the microwave domain based on the same irregularly shaped cavity with strong modal overlap that is massively parametrized by a 304-element-programmable metasurface. RSMs in our highly overdamped multiresonance transport problem are fundamentally intriguing because the simple critical coupling picture for reflectionless excitation of isolated resonances fails spectacularly. We show in simulation that the distribution of damping rates of scattering singularities broadens under strong absorption so that weakly damped zeros can be tuned toward functionalized RSMs.
我们通过实验证明，反射率为零的散射模式（RSMs）是相干完美吸收的广义版本，可以实现功能化，以执行反射率为零的可编程信号路由。我们实现了在操作频率和路由功能方面的多功能可编程性，并且在耦合时几乎没有反射，从而避免了射频或光子网络中的不必要的信号功率回波。我们报告了路由功能的现场观察结果，例如波长解复用，包括多通道激励需要适应相干输入波前的情况。所有实验均基于具有强模态重叠的相同不规则形状的腔在微波域中进行，该腔通过具有 304 个元素的可编程超材料进行了大规模参数化。我们在高度过阻尼多共振输运问题中对 RSMs 的研究非常有趣，因为对于孤立共振的反射率为零激发的简单临界耦合图像在很大程度上是失败的。我们在模拟中表明，散射奇点的阻尼率分布在强吸收下会变宽，因此可以将弱阻尼零点调谐到功能化的 RSMs。
