等离子体二聚体的光消光与近场特性：粒子形状和间距的作用
Optical extinction and near-field properties of plasmonic dimers: Role of particle shape and separation
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中文总结 AI 辅助
本研究采用贝塞尔型角参数化与不连续伽辽金时域有限元法，探究线偏振光激发下蝴蝶结纳米线二聚体的光学特性，对比不同几何结构与模型，分析几何参数对LSP及近场增强的影响，提出用雷达图评估非线性光学效应增强能力。
中文摘要 AI 辅助
金属纳米结构支撑的局域表面等离子体（LSP）在共振频率及相关空间场分布方面展现出极强的可调性，尤其纳米级间隙与尖角可实现可观的近场增强，适用于生化传感、纳米天线等应用。本研究探究线偏振光（包括偏振方向垂直于二聚体轴线）激发下蝴蝶结纳米线二聚体的光学特性，为区分二聚体间距与单体形状引发的效应，对比了蝴蝶结、圆柱状二聚体及三角线三种结构。本研究强调采用可调曲率的贝塞尔型角参数化的优势，并运用不连续伽辽金时域有限元法开展数值计算，以此识别杂化共振并系统分析几何参数的作用。针对所有研究的几何结构，本研究对比了空间局域德鲁德模型与空间非局域黑利维（Halevi）模型；以银为例，证明了黑利维模型捕捉的纵向非局域性会引发曲率依赖的LSP线移；对于高阶LSP，该非局域性会产生一系列可用于光捕获应用的共振。此外，本研究探究了与LSP共振相关的场增强，鉴于热点与冷点的同时出现，引入了依赖几何结构的指标以评估纳米结构增强非线性光学效应的能力，例如通过最优定位表面增强拉曼散射（SERS）活性分子；为便于同时研究这些指标，本研究提出采用合适的雷达图。
英文摘要
Localized surface plasmons (LSPs) supported by metallic nanostructures exhibit a great tunability of their resonance frequencies and associated spatial field distributions. In particular, nanoscale gaps and sharp corners exhibit promising near-field enhancements for applications such as biochemical sensing and nanoantennas. In this work, we investigate the optical properties of bowtie nanowire dimers excited by linearly polarized light, including polarization orthogonal to the dimer axis. To distinguish dimer-separation-induced and monomer-shape-induced effects, we compare bowtie, circular-cylindrical dimer and triangular wires. We emphasize the advantages of a Bézier-type corner parametrization with tunable curvature and employ the discontinuous-Galerkin time-domain finite-element method for numerical calculations. This enables the identification of hybrid resonances and the systematic analysis of the role of geometrical parameters. For all investigated geometries, we compare the spatially local Drude model with the spatially nonlocal Halevi model. For the specific case of silver, we demonstrate quantitative curvature-dependent LSP line shifts arising from the longitudinal nonlocality captured by the Halevi model. For higher-order LSPs, this nonlocality gives rise to a sequence of resonances that may be exploited for light-harvesting applications. Furthermore, we investigate the field enhancement associated with LSP resonances and, motivated by the occurrence of both hot and cold spots, introduce geometry-dependent measures for assessing the ability of nanostructures to enhance nonlinear optical effects, such as through the optimal positioning of SERS-active molecules. To facilitate the simultaneous study these measures, we propose the use of suitable radar charts.
