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Semiconductor light source for optical coherence tomography

Optical coherence tomography (OCT) is an emerging medical imaging technology based on the coherent interference of light. Current use of O C T in clinical settings is limited by the lack of a suitable light source. This thesis describes the design of a new type of source for OCT, based on the GalnNAs semiconductor materials system. A semiconductor heterostructure consisting of several different quantum wells is discussed as a device for generating broadband (>100 nm) light in the near infrared (900-1500 nm). The use of temperature to control spectral shape and intensity is examined. Other aspects of device design are investigated, including models for quantum well emission and for the band gaps of dilute nitride semiconductors. Photoluminescence measurements are presented, providing a proof of principle demonstration of the source design. Emission centred at 1225 nm with a 195 nm bandwidth is achieved. The use of temperature to control inter-well carrier transfer is demonstrated and successfully modelled. Localization effects of nitrogen cluster states are shown to be greatly reduced in quantum well structures, as compared to bulk samples.