Non-Hermitian metasurfaces for the best of plasmonics and dielectrics
Non-Hermitian metasurfaces for the best of plasmonics and dielectrics
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DOI：
10.1364/ome.428469
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发表时间：
2021-07
影响因子：
2.8
通讯作者：
Frank Yang;A. Hwang;C. Doiron;G. Naik
中科院分区：
文献类型：
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作者：
Frank Yang;A. Hwang;C. Doiron;G. Naik
材料及其几何结构构成了设计纳米光子器件的工具。在过去，材料折射率的实部一直是设计新型器件的重点。吸收，或想象指数，被认为是一种不受欢迎的影响。然而，材料虚指数的巧妙分布为设计纳米光子器件提供了额外的自由度。非厄米光学提供了一个独特的机会，利用材料的吸收损失来实现非常规的物理效应。这些效应通常发生在称为异常点的能量简并附近，包括增强的灵敏度、单向不可见性和非平凡拓扑。在这项工作中，我们利用等离子体吸收损耗（或虚指数）作为非厄米被动奇偶时间对称超表面的设计参数。我们发现耦合的等离子体-光子谐振器对，在吸收损失上具有很大的不对称性，但在辐射损失上平衡，在特殊点上表现出光学相变和定向散射。这些系统为使用相位、对称和拓扑作为强大工具的超表面设计提供了新的途径。
Materials and their geometry make up the tools for designing nanophotonic devices. In the past, the real part of the refractive index of materials has remained the focus for designing novel devices. The absorption, or imaginary index, was tolerated as an undesirable effect. However, a clever distribution of imaginary index of materials offers an additional degree of freedom for designing nanophotonic devices. Non-Hermitian optics provides a unique opportunity to take advantage of absorption losses in materials to enable unconventional physical effects. Typically occurring near energy degeneracies called exceptional points, these effects include enhanced sensitivity, unidirectional invisibility, and non-trivial topology. In this work, we leverage plasmonic absorption losses (or imaginary index) as a design parameter for non-Hermitian, passive parity-time symmetric metasurfaces. We show that coupled plasmonic-photonic resonator pairs, possessing a large asymmetry in absorptive losses but balanced radiative losses, exhibit an optical phase transition at an exceptional point and directional scattering. These systems enable new pathways for metasurface design using phase, symmetry, and topology as powerful tools.