In this work, resonant laser spectroscopy has been utilized in two major projects --resonance fluorescence measurements in solid-state quantum-confined nanostructures and laser-induced fluorescence measurements in gases. The first project focuses on studying resonant light-matter interactions in semiconductor quantum dots "artificial atoms" with potential applications in quantum information science. Of primary interest is the understanding of fundamental processes and how they are affected by the solid-state matrix. Unlike atoms, quantum dots are susceptible to a variety of environmental influences such as phonon scattering and spectral diffusion. These interactions alter the desired properties of the scattered light and hinder uses in certain single photon source applications. One application of current interest is the use of quantum dots in “quantum repeaters” for which two-photon interference is key. Motivated by such an application we have explored the limits imposed by environmental effects on two quantum dots in the same sample, the scattered light from which is being interfered. We find that both one-photon and two-photon interference, although substantial, are affected in a variety of ways, in particular by spectral diffusion. These observations are discussed and compared with a theoretical model. We further investigated correlations in pulsed resonance fluorescence, and found significant unexpected spectral and temporal deviations from those studied under continuous wave excitation. Under these conditions, the scattered light exhibits Rabi oscillations and photon anti-bunching, while maintaining a rich spectrum containing many spectral features. These observations are discussed and compared with a theoretical model. In the second project, the focus is on the investigation of the possibility of detecting N2+ ions in air using laser induced fluorescence, with potential applications in detection of fissile materials at a distance. A photon-counting analysis reveals that the fluorescence decay rate rapidly increases with increasing N2 pressure and thus limits the detection at elevated pressures, in particular at atmospheric pressure. We show that time-gated detection can be used to isolate N2+ fluorescence from delayed N2 emission. Based on the spontaneous Raman signal from N2 simultaneously observed with N2+ fluorescence, we could estimate a limit of detection in air of order 108-1010 cm3.
| Identifer | oai:union.ndltd.org:USF/oai:scholarcommons.usf.edu:etd-7724 |
| Date | 18 November 2016 |
| Creators | Konthasinghe, Kumarasiri |
| Publisher | Scholar Commons |
| Source Sets | University of South Flordia |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Graduate Theses and Dissertations |
| Rights | default |
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