## Self-Similarity of Plasmon Edge Modes on Koch Fractal Antennas

journal contribution

posted on 30.10.2017, 00:00 by Edson
P. Bellido, Gabriel D. Bernasconi, David Rossouw, Jérémy Butet, Olivier J. F. Martin, Gianluigi A. BottonWe
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.

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Koch snowflake fractal geometriessurface integral equation methodedge modesPlasmon Edge Modessilver strip antennasKoch snowflake fractalsedge unitsfractal structuressilver Koch fractal antennasplasmon edge modesMultiple surface plasmon edge modeselectron energy loss spectroscopyKoch Fractal Antennasself-similar segments

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### Categories

### Keywords

Koch snowflake fractal geometriessurface integral equation methodedge modesPlasmon Edge Modessilver strip antennasKoch snowflake fractalsedge unitsfractal structuressilver Koch fractal antennasplasmon edge modesMultiple surface plasmon edge modeselectron energy loss spectroscopyKoch Fractal Antennasself-similar segments