In this work, we propose a simple scheme to realize an acoustic coherent perfect absorber (CPA) and laser modes by embedding a non-Hermitian dopant in a zero index metamaterial. When the dopant is filled with a loss medium at a specific level, the sample can absorb the incident waves completely. On the other hand, when the dopant is filled with a gain medium, the sample can act as a laser oscillator to boost the incident waves. The theoretical derivation based on the scattering matrix and the numerical simulation based on the finite element method are performed and both show good agreement with each other. We also discover that the CPA and laser modes are very sensitive and can be controlled by adjusting the structure parameters or the relative phase of the incident waves. Moreover, the case that asymmetric incidences have different beam widths is considered. We envision that our work may have potential applications in designing acoustic devices, such as absorbers, transducers, and receivers.

中文翻译：

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通过零折射率超材料中的非厄米掺杂剂实现声相干完美吸收器和激光模式

在这项工作中，我们提出了一种简单的方案，通过在零折射率超材料中嵌入非厄米掺杂剂来实现声相干完美吸收器 (CPA) 和激光模式。当掺杂剂填充特定水平的损耗介质时，样品可以完全吸收入射波。另一方面，当掺杂剂充满增益介质时，样品可以作为激光振荡器来增强入射波。进行了基于散射矩阵的理论推导和基于有限元方法的数值模拟，两者均表现出良好的一致性。我们还发现 CPA 和激光模式非常敏感，可以通过调整结构参数或入射波的相对相位来控制。而且，考虑了非对称入射具有不同光束宽度的情况。我们设想我们的工作可能在设计声学设备方面具有潜在的应用，例如吸收器、换能器和接收器。