richard taubert FROM NEAR-FIELD TO FAR-FIELD: plasmonic coupling in three-dimensional nanostructures From Near-Field to Far-Field: Plasmonic Coupling in Three-Dimensional Nanostructures

This thesis provides a comprehensive study of the coupling phenomena that occur in plasmonic nanostructures. Electromagnetic coupling between metallic nanoparticles leads to strong spectral modifications in the structures, which are determined using linear optical spectroscopy in the visible and infrared wavelength range. In contrast to previous investigations, the key aspect here are the properties of plasmonic farfield coupling in three-dimensionally arranged structures. These are fabricated by electron beam lithography in a multilayer process, which allows for a three-dimensional arrangement of plasmonic particles. We study coupling in a plasmonic dimer for different arrangements. In order to address the transition from the near-field to the far-field regime, we investigate a structure consisting of two nanowires stacked on top of each other for a wide range of interparticle spacings, and thus are able to examine nearas well as far-field coupling effects. In case of near-field coupling, only the quasistatic near fields of the plasmonic structures are important and the plasmon hybridization scheme gives an excellent qualitative description of all the observed phenomena. In contrast, the far-field regime is characterized by the occurrence of FabryPérot modes due to the large vertical spacing between the particles. These couple to the particle plasmon resonances, forming new coupled modes which are extensively discussed. A situation of particular interest occurs whenever the interparticle distance fulfills the Bragg criterion, i. e., the vertical distance equals a multiple of half the particle plasmon resonance wavelength: then the coupledmode which spectrally approaches the single layer particle plasmon resonance becomes dark and a broad region of high reflectance forms. Increasing the number of oscillators stacked at this particular distance leads to the increase of the spectral width of the plasmonic response and the formation of a broad photonic band gap, which spans about one octave in the optical wavelength regime. In contrast to previous similar investigations which were carried out with semiconductor quantum well structures or atoms in optical lattices, the plasmonic particles exhibit an extraordinarily strong coupling to the light field. Therefore, we are able to explore the regime where the coupling between