Extraction of light from a quantum emitter by tailoring the photonic environment

Research output: Book/ReportPh.D. thesis

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Abstract

Since the discovery of quantum mechanics it has been a physicists dream to test and exploit the fantastic prediction of entanglement. Applications based on entanglement are quantum key distribution and quantum computing which can exploit ying quantum bits based on single photons. To deterministicly create this type of quantum bits single photons on demand are essential. This thesis presents the work on controlling the photonic environment of a quantum emitter in order to effciently extract photons.
We demonstrate increased photon collection effciencies from single nitrogen vacancy (NV) centers by a factor of up to 1.76 when approaching it with a plane silver mirror made on an optical fiber facet. However, using this method we also show that the non-radiative decay rate of NV centers can be highly dependent on the excitation power, which makes this method a poor broadband approach for obtaining information on the photonic decay rate of the NV center. By further spectrally resolving emission from these systems we observe clear modulations which carry information related to the photonic decay rate where the quantum effciency can be deduced from.
We carry out three experiments where coupling NV centers to the highly confined mode fields of silver nano-wires (SNWs) are exploited. First, we demonstrate routing of single plasmons fed by a single NV center. Controlled routing is shown by facilitating different beamsplitter configurations where the routing itself is performed on a length scale less than 2 µm.
We then measure the coupling between an NV center ensemble and single SNWs through 2-dimensional imaging of the NV center lifetime which outlines the SNW profiles confirmed by atomic force microscopy (AFM). Finally, an attempt to couple a single SNW to NV centers in a micro-fabricated diamond nano-pillar is presented.
The final part of the thesis address experiments on coupling colloidal quantum dots (CQDs) to the gap mode of two Si3N4 waveguides (DSNWs). We demonstrate evanescent-field coupling between spin-coated CQDs and the waveguide. However we are unable to deduce the coupling-related modification of the CQD lifetime due to apparent density dependent CQD interactions which dominate the lifetime distribution. We circumvent this by instead attaching CQDs to an AFM cantilever and scanning this across the DSNWs. By doing this, we obtain a 2-dimensional lifetime map showing an AFM-confirmed outline of the DSNW through the spatially-dependant lifetime variations.
Original languageEnglish
Place of PublicationKongens Lyngby
PublisherTechnical University of Denmark
Number of pages165
Publication statusPublished - 2015

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