Angle-Resolved Spectroscopy of Resonant Nanostructures: Metasurface Fabrication and Dipolar Orientation Analysis

Abstract

Two topics are researched in this thesis, which heavily rely on the angular analysis of plasmonic optical responses. The first major section highlights the fabrication and analysis of nanopyramids using nanosphere lithography and electron beam lithography, showing how various nanopyramid shapes influence resulting plasmonic modes. Simulations and multipole decomposition analysis reveal that 3D stand-alone nanopyramids support complex radiation patterns which are successfully decoded. Arranged in a 2D hexagonal grating while being connected by a continuous gold film, they additionally support photonic states such as surface lattice resonances and surface plasmons. The resulting metasurfaces exhibit narrow surface lattice resonance linewidths, as well as Rayleigh anomaly surface plasmon modes, enabling enhanced scattering and Raman signal applications. In the second section, a new and non-destructive spectropolarimetric method is developed to accurately determine the azimuthal orientation of dipole moments in plasmonic nanostructures, regardless of aspect ratio or asymmetry. Using a minimal number of spectra, theoretical modeling, and advanced computation including assistance from machine learning algorithms, this robust approach reliably extracts dipole orientations without damaging the inspected samples. The technique is broadly applicable, from chiroptical spectroscopy to metasurface research and precision 2D material stacking.

Dissertation ist gesperrt bis 21. September 2027 !