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Defence of dissertation in the field of engineering physics, Aaro Väkeväinen, M.Sc.(Tech.)

Generation of coherent light in nanometer scale metallic structures

Title of the dissertation is "Lasing and Bose-Einstein condensation in plasmonic lattices at weak and strong coupling regimes".

Plasmonics studies the optical interaction in metallic nanostructures and how these structures can be utilized for concentrating, manipulating and guiding light in dimensions below the diffraction limit. In this dissertation, the author has experimentally studied strong light-matter interaction and generation of coherent light in metallic nanoparticle arrays combined with organic dye molecules.

The dissertation presents results on strong coupling between plasmonic lattice resonances and dye molecules. Strong coupling alters the quantum states of the involved physical entities and can thus modify chemical reactions. By optical excitation of the molecules, laser action is achieved. The samples generate spatially and temporally coherent laser pulses that have a duration of only one trillionth of a second. Under certain conditions, quasiparticles that are partly light and partly matter are shown to form a Bose-Einstein condensate, which also results in coherent light pulses but is different from traditional laser action. A Bose-Einstein condensate describes a quantum state where a large number of particles behave in concert as if they were only a single particle.

In this dissertation, Bose-Einstein condensation is demonstrated for the first time in plasmonic nanoparticle arrays, and at both weak and strong coupling regimes. The room-temperature operation, significant robustness and high luminescence of the samples provide an excellent platform for future fundamental studies of non-equilibrium dynamics of quantum systems. The condensation phenomenon may eventually find applications in optical data processing and in some areas of emerging quantum technologies.

Opponent: Professor Lukas Novotny, ETH Zürich, Switzerland

Custos: Professor Päivi Törmä, Aalto University School of Science, Department of Applied Physics

Contact information: Aaro Väkeväinen, Microsoft HoloLens, [email protected],
tel. 050 400 7348

Electronic dissertationThe dissertation is publicly displayed 10 days before the defence at the noticeboard of the School of Science in Konemiehentie 2, Espoo.

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