Date of Award

2021

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Department

Physical Science

First Advisor

Dr Svetlana Slepneva

Second Advisor

Dr Guillaume Huyet

Abstract

Swept Sources are lasers with a periodically modulated frequency, over a wide scanning range. They are widely used in Optical Coherence Tomography (OCT) for medical imaging and metrology. The narrow instantaneous linewidth of a swept source is required for longer OCT imaging depths. The goal of the project is to investigate the mechanism that deteriorates the coherence of a swept-source laser by analyzing its properties under external injection and investigate the possibilities for a phase-locked laser operation, in order to control the coherence properties. The laser under study was a semiconductor ring fiber-based cavity laser, incorporating a tunable narrow transmission bandwidth optical filter. The properties of the laser were analyzed in the regime of a fixed wavelength and in a slow filter sweeping regime. Above the lasing threshold, the laser exhibited periodic stable power dropouts. These drops are similar to the stable Nozaki-Bekki holes (NBH) described in Complex Ginsburg-Landau equation. The origin of the drops is attributed to the presence of the alpha factor, inherent to the semiconductor material of the gain medium, the finite filter transmission bandwidth and the injection current. The properties of the holes were also investigated as a function of the bias current, transmission wavelength, and the filter sweep. The coherent optical injection was applied, and the possibility of locking was demonstrated, however, the locking regime could only be observed over a short period of time, due to the drift of the filter transmission. The incoherent optical injection was applied to localize the holes and study their dynamics.

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Access Level

info:eu-repo/semantics/openAccess

Included in

Physics Commons

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