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Self-Similarity of Plasmon Edge Modes on Koch Fractal Antennas
ACS Nano ( IF 15.8 ) Pub Date : 2017-11-08 00:00:00 , DOI: 10.1021/acsnano.7b05554
Edson P. Bellido 1 , Gabriel D. Bernasconi 2 , David Rossouw 1 , Jérémy Butet 2 , Olivier J. F. Martin 2 , Gianluigi A. Botton 1
Affiliation  

We investigate the plasmonic behavior of Koch snowflake fractal geometries and their possible application as broadband optical antennas. Lithographically defined planar silver Koch fractal antennas were fabricated and characterized with high spatial and spectral resolution using electron energy loss spectroscopy. The experimental data are supported by numerical calculations carried out with a surface integral equation method. Multiple surface plasmon edge modes supported by the fractal structures have been imaged and analyzed. Furthermore, by isolating and reproducing self-similar features in long silver strip antennas, the edge modes present in the Koch snowflake fractals are identified. We demonstrate that the fractal response can be obtained by the sum of basic self-similar segments called characteristic edge units. Interestingly, the plasmon edge modes follow a fractal-scaling rule that depends on these self-similar segments formed in the structure after a fractal iteration. As the size of a fractal structure is reduced, coupling of the modes in the characteristic edge units becomes relevant, and the symmetry of the fractal affects the formation of hybrid modes. This analysis can be utilized not only to understand the edge modes in other planar structures but also in the design and fabrication of fractal structures for nanophotonic applications.

中文翻译:

科赫分形天线上的等离激元边缘模式的自相似性。

我们研究科赫雪花分形几何体的等离子体行为及其作为宽带光学天线的可能应用。光刻定义的平面银Koch分形天线已制成,并使用电子能量损耗光谱法以高空间和光谱分辨率进行了表征。用表面积分方程法进行的数值计算为实验数据提供了支持。分形结构支持的多个表面等离激元边缘模式已经成像和分析。此外,通过隔离和再现长银带状天线中的自相似特征,可以识别出现在科赫雪花分形中的边缘模式。我们证明了分形响应可以通过称为特征边缘单元的基本自相似段的总和来获得。有趣的是,等离子体激元边缘模式遵循分形缩放规则,该规则取决于分形迭代后结构中形成的这些自相似片段。随着分形结构的尺寸减小,特征边缘单元中的模耦合变得重要,并且分形的对称性影响混合模的形成。这种分析不仅可以用来理解其他平面结构中的边缘模式,而且可以用于纳米光子应用的分形结构的设计和制造。
更新日期:2017-11-08
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