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Title: Hybrid quantum well/quantum dot structure for broad spectral bandwidth emitters
Author: Chen, Siming
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2014
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This thesis details a hybrid quantum well (QW)/quantum dot (QD) active element for an application in broadband source. First of all, a literature review on the fundamentals of optical coherence tomography (OCT) and superluminescent light emitting diodes is provided in Chapter 1. Basic principles of QD formation using molecular beam epitaxy and several experimental techniques are reviewed in Chapter 2. The first vertically integrated hybrid QW/QD structure for application in broadband light sources is proposed in Chapter 3. Spontaneous emission from both the QW and the QDs resulted in a full width half maximum (FWHM) of 250nm being demonstrated. In Chapter 4, experimental results on the modal gain and lasing characteristic of hybrid QW/QD laser are described. Due to the contribution from the QD ground state and first excited state, and the lowest energy transition of the QW, the modal gain at room temperature is extended to 300nm. The values for modal gain are further confirmed by simultaneous three state lasing. The first hybrid QW/QD superluminescent diode is discussed in Chapter 5. High order QW transitions are observed at high current densities. As a result, a 3dB emission spectrum of FWHM linewidth of 289nm centered at ~1200nm with a corresponding power of 2.4mW is achieved. The origin of high order QW transitions is discussed in Chapter 6. New device designs utilizing a larger number of QD layers with higher areal density and larger state separation is reported in Chapter 7. Chapter 8 summarizes the whole thesis.
Supervisor: Hogg, Richard Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available