The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ.
ACS Nano. 2011 Apr 26;5(4):3293-308. doi: 10.1021/nn200438e. Epub 2011 Mar 18.
The interaction between metallic nanowires and a metal substrate is investigated by means of transformation optics. This plasmonic system is of particular interest for single molecule detection or nanolasers. By mapping such a plasmonic device onto a metal-insulator-metal infinite structure, its optical response can be fully derived analytically. In this article, the absorption cross-section of a nanowire placed close to a metallic surface is derived within and beyond the quasi-static limit. The system is shown to support several modes characterized by a different angular momentum and whose resonance red-shifts when the nanoparticle approaches the metal substrate. These resonances give rise to a drastic field enhancement (>10(2)) within the narrow gap separating the nanoparticle from the metal surface. The case of a nanowire dimer is also investigated and is closely related to the previous configuration. More physical insights are provided especially with respect to the invisibility dips appearing in the radiative spectrum. Numerical simulations have also been performed to confirm our analytical predictions and determine their range of validity.
采用变换光学研究了金属纳米线与金属衬底之间的相互作用。这种等离子体系统对于单分子检测或纳米激光器特别感兴趣。通过将这种等离子体器件映射到金属-绝缘体-金属无限结构上，可以对其光学响应进行全面的解析推导。本文推导了在准静态极限内和之外，靠近金属表面的纳米线的吸收截面。结果表明，该系统支持多种模式，其模式的角动量不同，并且当纳米粒子接近金属衬底时，共振会红移。这些共振在纳米粒子与金属表面之间的狭窄间隙内产生了剧烈的场增强（>10(2)）。还研究了纳米线二聚体的情况，它与前面的配置密切相关。特别是在辐射光谱中出现的隐形谷方面，提供了更多的物理见解。还进行了数值模拟以验证我们的分析预测并确定它们的有效范围。
