Arumona Arumona Edward, Czajkowski Krzysztof M, Antosiewicz Tomasz J
Opt Express. 2023 Jul 3;31(14):23459-23474. doi: 10.1364/OE.494389.
Hyperbolic nanoresonators, composed of anisotropic materials with opposite signs of permittivity, have unique optical properties due to a large degree of freedom that hyperbolic dispersion provides in designing their response. Here, we focus on uniaxial hyperbolic nanoresonators composed of a model silver-silica multilayer in the form of spheroids with a broad aspect ratio encompassing both prolate and oblate particles. The origin and evolution of the optical response and mode coupling are investigated using both numerical (T-matrix and FDTD) and theoretical methods. We show the tunability of the optical resonances and the interplay of the shape and material anisotropy in determining the spectral response. Depending on the illumination conditions as well as shape and material anisotropy, a single hyperbolic spheroid can show a dominant electric resonance, behaving as a pure metallic nanoparticle, or a strong dipolar magnetic resonance even in the quasistatic regime. The quasistatic magnetic response of indicates a material-dependent origin of the mode, which is obtained due to coupling of the magnetic and electric multipoles. Such coupling characteristics can be employed in various modern applications based on metasurfaces.
双曲线纳米谐振器由具有相反介电常数符号的各向异性材料组成，由于双曲线色散在设计其响应时提供了很大的自由度，因此具有独特的光学特性。在这里，我们重点研究由模型银 - 二氧化硅多层组成的单轴双曲线纳米谐振器，其呈球体形式，具有涵盖长球体和扁球体颗粒的宽纵横比。使用数值方法（T矩阵和时域有限差分法）和理论方法研究了光学响应和模式耦合的起源与演变。我们展示了光学共振的可调性以及形状和材料各向异性在确定光谱响应中的相互作用。根据照明条件以及形状和材料各向异性，单个双曲线球体可以表现出主导的电共振，表现为纯金属纳米颗粒，或者即使在准静态状态下也能表现出强偶极磁共振。准静态磁响应表明该模式起源于与材料相关的因素，这是由于磁多极子和电多极子的耦合而获得的。这种耦合特性可用于基于超表面的各种现代应用中。
