亚波长双曲结构的多频超散射
Multifrequency superscattering from subwavelength hyperbolic structures
摘要：
超散射，即，来自亚波长物体的散射截面超过单通道极限的现象在增强的传感/光谱学、太阳能电池和生物医学成像中具有重要的前景。超散射通常只能在单一频率范围内构建，并且严重依赖于不可避免的材料损耗。在这样的现实条件下，超散射还没有被预测，也没有观察到同时存在于多个频率制度。在这里，我们介绍了多频超散射的亚波长双曲线结构，它可以由人工超材料或天然存在的材料，如六方氮化硼（BN），并显示这种双曲线材料的优势，以减少结构的复杂性。其基本机制是由于声子-极化激元的特殊色散引起的BN中出现的多频率区域的多模共振。重要的是，多频超散射对材料损耗和一些结构变化具有很高的耐受性，使多频超散射的概念更接近有用和现实的条件。
英文摘要：
Superscattering, i.e., a phenomenon of the scattering cross section from a subwavelength object exceeding the single-channel limit, has important prospects in enhanced sensing/spectroscopy, solar cells, and biomedical imaging. Superscattering can be typically constructed only at a single frequency regime, and depends critically on the inescapable material losses. Under such realistic conditions, superscattering has not been predicted nor observed to exist simultaneously at multiple frequency regimes. Here we introduce multifrequency superscattering in a subwavelength hyperbolic structure, which can be made from artificial metamaterials or from naturally-existing materials, such as hexagonal boron nitride (BN), and show the advantage of such hyperbolic materials for reducing structural complexity. The underlying mechanism is revealed to be the multimode resonances at multiple frequency regimes as appear in BN due to the peculiar dispersion of phonon-polaritons. Importantly, the multifrequency superscattering has a high tolerance to material losses and some structural variations, bringing the concept of multifrequency superscattering closer to useful and realistic conditions.
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