Title: Plasmonic antenna design and in-line holographic imaging for biological applications
Other Titles: Plasmonische antenna design en holografische meting voor biologische toepassingen
Authors: Vercruysse, Dries
Issue Date: 15-Apr-2015
Abstract: The way in which light interacts with a microscopic object is indicative of the object itself and its surroundings. Optical sensors use this, either to identify the object or to probe the small volumes around known structures. In the latter case, the structure serves as a nanoantenna, transferring a signal from the nano-scale onto light. Much research is devoted to understanding how these nanoantennas interact with light and how their geometry can be optimized for its intended function.
In this thesis we investigate and design radiation properties of microscopic objects. Nano-sized metal V-shaped antennas form the initial focus of our study and are shown to scatter light laterally in one direction. The directional scattering pattern occurs at a Fano interference between two localized surface plasmon modes of the antenna. Using finite-difference time-domain simulations and eigenmode analysis, the interference mechanisms are fully elucidated by the charge distribution of the antenna's oscillation, as well as by looking at interfering surface plasmon modes. In addition to scattering, the emission of a quantum emitter, e.g. a fluorescent molecule, near the V-antenna is also investigated and found to generate directional radiation patterns as well. The emission direction, however, appears to oppose the scattering direction, suggesting that the underlying mechanism might differ from that of scattering. A thorough eigenmode analysis confirms this, and shows how the directional emission originates from the interference between a single mode and uncoupled light from the quantum emitter. These findings are, subsequently, employed in a more functional manner. The V-antenna is evaluated as a directional coupler to optical waveguide, and the established interference mechanisms are used to construct and fine tune a new single particle color router, based on a split ring resonator geometry.
At the end of this thesis, rather than designing a scatterer for a certain scatter pattern, we also try to identify a scatterer by its scatter pattern. A compact holographic setup is constructed to collect these patterns from white blood cells, and a scale space recognition algorithm is developed to identify the cells as one of there main three subtypes based on the reconstruction of the hologram.
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Solid State Physics and Magnetism Section

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