发表机构
University of Maryland, College Park（马里兰大学帕克分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出散射矩阵奇异性是众多非厄米散射现象的统一基础，通过少量可调参数即可在任意频率创造并控制这些奇异性，并演示了相干完美吸收，实现极低输出输入功率比。
AI 中文摘要
可控地操纵非厄米波散射环境的能力已被用于发现奇异散射现象，如散射奇异点和相干完美吸收，并催生了众多应用，包括信号路由、滤波、成像、传感、无线能量传输等。我们引入了一个概念，即这些应用和现象从根本上受散射矩阵奇异性的支配。基于这一理解，我们所展示的控制散射奇异性位置的能力可用于增强现有应用并开发新应用。在一般的复杂散射系统中，存在大量拓扑保护的散射奇异性，对应于散射矩阵各种函数的复零点。我们证明，仅用三个可调参数，就能在此类系统中任意频率处为几乎任何散射奇异性创造条件。利用五个可调参数，我们展示了可以实现更复杂的场景，例如使不同的奇异性重合或将奇异性置于不同频率。具有可调参数的系统的优势在于，通用复杂系统可以通过仅重新配置其可调参数而被重新利用以展现许多不同的有用特性。一个特别有趣的散射现象是相干完美吸收，其中注入系统的特定波前被完全吸收，没有任何能量通过任何通道反射或透射。在为任意预选频率的该奇异性创造条件后，我们可以找到并注入相干完美吸收波前，并演示在具有两个、三个和四个端口的四分之一蝴蝶结台球中，输出与输入功率比分别低至1x10^{-10}、2x10^{-8}和3x10^{-8}。
英文摘要
The ability to controllably manipulate non-Hermitian wave scattering environments has been used to discover exotic scattering phenomena such as scattering exceptional points and coherent perfect absorption, and create numerous applications including signal routing, filtering, imaging, sensing, wireless power transfer, etc. We introduce the concept that many of these applications and phenomena are fundamentally governed by singularities of the scattering matrix. With this understanding, our demonstrated ability to control the location of scattering singularities can be used to enhance current applications and develop new ones. In generic complex scattering systems, there is an abundance of topologically protected scattering singularities corresponding to complex zeros of various functions of the scattering matrix. We show that with just three tunable parameters we are able to create the conditions for nearly any scattering singularity at arbitrary frequencies in such systems. With five tunable parameters, we demonstrate that more complex scenarios can be accomplished, such as making disparate singularities coincident or placing singularities at different frequencies. A benefit of systems with tunable parameters is that generic complex systems can be re-purposed into exhibiting many different useful properties solely by reconfiguring their tunable parameters. A particularly interesting scattering phenomenon is coherent perfect absorption, where a specific wavefront injected into the system is completely absorbed, with no energy reflected or transmitted through any channel. After creating the conditions for this singularity at an arbitrary preselected frequency, we can find and inject the coherent perfect absorption wavefront and demonstrate output-to-input power ratios as low as 1x10^{-10}, 2x10^{-8}, and 3x10^{-8} in a quarter bowtie billiard with two, three, and four ports, respectively.
