Abstract:
Fourier domain mode locked lasers are a new class of fiber based swept source laser designed originally for use as broadband light sources in optical coherence tomography (OCT). Since then however there has been considerable interest in their application and FDML lasers are being applied to an ever increasing number of fields. The primary field that motivated their development, OCT, is an interferometric technique with mm resolution that is currently capable of producing volumetric images of tissue and microstructures in near real time. FDML lasers were developed for a mode of OCT imaging known as swept-source OCT, in which the output wavelength sweeps over the FDML lasers total bandwidth in a fixed pattern. Swept-source OCT demands that light sources have a high degree of sweep to sweep stability and coherence, high output power and above all, an extremely fast sweep rate. In this thesis we investigate FDML lasers at 1550 nm and present a new cavity design incorporating dispersion shifted fiber (DSF). Also covered is design information such as picking components, and simple measurements that allow the laser to operate correctly in the FDML regime. Typical performance of the operational laser will be presented. A discussion of dispersion is also presented in context of its effect on the operation of an FDML laser, the sources from which it arises in the cavity and how dispersion is compensated in a practical FDML cavity. As the influence of dispersion in FDML is not entirely understood at present, a measurement will be made that attempts to quantify the wavelength mismatch and thus dispersive properties of key cavity elements.
