Evolutionary Design of Plasmonic Nanoantennas for Multispectral Applications

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Perustieteiden korkeakoulu | Master's thesis
Optiikka ja molekyylimateriaalit
Degree programme
iv + 90 s. + liitt. 12 s.
Nanoantennas are used to control light on the nanoscale in a wide range of applications. However, the interaction mechanisms between light and plasmonic structures are complex and, therefore, the design of a nanoantenna for a given application is not straightforward. Analytical methods are scarce and typically only valid for simple problems. Therefore, more generic approaches are indispensable for the design of complex nanoantennas that are subject to multiple conflicting requirements, such as those for multispectral applications. In this thesis, a generic method is developed for the design of plasmonic nanoantennas, subject to arbitrary requirements. The method combines a binary genetic optimization algorithm with a finite-difference time-domain (FDTD) solver. In principle applicable to a wide range of structures, the method is implemented and tested for the design of planar checkerboard-like nanostructures. Specifically, the method is demonstrated for the design of a gold nanoantenna exhibiting opposed responses for two different selected wavelengths: the nanoantenna is required to enhance the field at the center of the structure for the first wavelength, while being transparent at the second wavelength. By independently calculating the electromagnetic response of the gold nanoantennas at both wavelengths, a multiobjective optimization is performed. The structures generated throughout the optimization are used to find an approximation of the Pareto front. The optimal structure is presented, together with an analysis which determines the most important geometric parts of the structure for optimal functioning of the antenna. The presented results validate the method and show its potential in the design of structures for novel applications, both for single and multiple wavelengths
Kaivola, Matti
Thesis advisor
Moerland, Robert
plasmonic nanoantennas, multispectral applications, cloaking, genetic optimization algorithm
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