AI 中文总结
本研究探究非同心多壳纳米线的几何结构对其等离激元响应的影响，通过解析与数值模拟揭示非同心性可调控等离激元杂化与近场局域，为纳米光场调控提供新途径。
AI 中文摘要
多壳纳米结构中的局域表面等离激元（LSPs）为纳米尺度光场调控提供了通用途径，但偏离同心几何结构的影响尚未得到充分理解。本研究探讨了壳层非同心性对单芯单壳及多壳纳米线准静态光学响应的影响。利用双极坐标的保角特性，推导了非同心圆柱界面的解析解，并系统分析了LSP共振、吸收光谱及近场分布的演化。从单壳结构出发，结果表明非同心性可使入射辐射与高阶等离激元模式发生有限耦合，而这类模式在同心结构的准静态极限下无光学活性。将分析扩展至多壳“靶心”纳米线后，明确了壳层厚度、固定厚度壳单元数量（每个单元定义一组介质壳与金属壳）以及界面非同心性如何塑造杂化等离激元光谱：增加金属-介质界面数量可拓宽光谱响应，而非同心几何结构还能增加可及共振的密度，并优先将电磁场局域在较薄壳段及其周围。最终，基于Mie理论对同心结构、受多普勒光栅启发的非同心“靶心”纳米线，以及全波不连续伽略金时域模拟的对比，可评估典型纳米线尺寸下非同心性的影响。这些结果为几何诱导的等离激元杂化提供了认识，并为主动纳米光子学及等离激元辅助光化学应用的纳米尺度光能量局域调控提供了途径。
英文摘要
Localized surface plasmons (LSPs) in multi-shell nanostructures provide a versatile route for controlling optical fields at the nanoscale, yet the influence of deviations from concentric geometries remains insufficiently understood. Here, we investigate the impact of shell nonconcentricity on the quasistatic optical response of core-single-shell and core-multi-shell nanowires. Exploiting the conformal properties of bipolar coordinates, we derive analytical solutions for nonconcentric cylindrical interfaces and systematically analyze the evolution of LSP resonances, absorption spectra, and near-field distributions. Starting from single-shell structures, we show that nonconcentricity enables finite coupling of incident radiation to higher-order plasmon modes that are optically inactive in the quasistatic concentric limit. Extending the analysis to multi-shell bull's eye wires, we identify how shell thickness, number of fixed-thickness shell units, each defining a set of a dielectric and metal shell, as well as interface nonconcentricness shape the hybridized plasmon spectrum. Increasing the number of metal-dielectric interfaces broadens the spectral response, while nonconcentric geometries additionally increase the density of accessible resonances and localize electromagnetic fields preferentially within and around the thinner shell sections. Eventually, comparison of concentric with bipolar and Doppler-grating-inspired nonconcentric bull's eye wires based on Mie theory and full-wave Discontinuous Galerkin Time-Domain simulations, respectively, allows to assess the impact of nonconcentricness for typical nanowire dimensions. These results provide insight into geometry-induced plasmon hybridization and suggest routes toward nanoscale control of optical energy localization for applications in active nanophotonics and plasmon-assisted photochemistry.
Comments23 pages, 10 figures
