PhD Defense by Eran Kot – Niels Bohr Institute - University of Copenhagen

Niels Bohr Institute > Calendar > 2012 > PhD Defense by Eran Kot

PhD Defense by Eran Kot

Efficient interfacing of light and surface plasmon polaritons for quantum optics applications

The research of light and matter interactions is the most fascinating and powerful tool in advancing our understanding of both atomic and light physics.  However, generating and controlling strong coherent interaction between normally very weakly interacting light and quantum emitters proves a difficult task. By exploiting the strong confinement of light in a surface plasmon mode, a cavity-free, broadband tool can be designed to engineer the light-emitter interaction in the vicinity of metallic nano-structures. These surface plasmons, hybrid waves of light and electronic oscillations propagating on the surface of metals have been shown to be useful in coupling to quantum dots, nanodiamond NV-centers defects and other quantum emitters. However, being lossy these modes need to be efficiently coupled out to photons in order to facilitate experimental control of the system.  In this work we studied the interaction of surface plasmons on nanometallic structures and light. We suggest two configurations in which efficient coupling to the surface plasmon modes can be achieved on the nanoscale, allowing the transfer of single photons from one mode to the other. The first, applicable to plasmonic guides, exploits the phenomena of adiabatic following to transfer the plasmonic excitation to an adjacent photonic waveguide by slowly tapering the plasmonic guide into and then out of resonance with the photonic guide. For this end we develop a general perturbative description for guides of arbitrary cross section, and go on to apply it to slab guides showing up to 90% coupling efficiencies for realistic experimental parameters. The second coupling configuration suggested is a plasmonic coupling lens, constructed around the emitter in a proximity to a metallic interface. Concentric grating rings then couple light propagating normal to the surface to a inward propagating plasmons, showing coupling efficiencies of ~70% and enhancement of the emitters decay rate by up to 45 times that of the isolated emitter's decay rate. Finally, we explored a nonclassicality criterion for the state of a continuous variable, local system. This is done by inferring the breakdown of classical models from quadrature measurements, expressed as the lack of a proper distribution function of the underlying generalized coordinates. This provides a useful tool in characterizing new candidate systems for quantum applications and by its simplicity, also furthers the understanding of the quantum-classical transition.