Bidirectional mode-locked fiber ring laser
In modern day world, advances in technology are constantly pushing the limits of improvement in measurement accuracy. With each passing year, government agencies and contract companies increase investment in research of high precision, ultra sensitive, instruments. Over the last decade, advancements in ultrashort time scale optics have moved the field of metrology to the quantic realm. At this new scientific frontier, mode-locked lasers, with ultra sensitive phase measurement capabilities, have been playing an increasingly significant role. Among these highly sophisticated systems, mode-locked fiber lasers have been extensively explored in an unidirectional mode, while bidirectional remains a promising source for applications with considerable space for experimental innovation. In this project, efforts have been made to contribute to the scientific achievements in this area, with the implementation of an innovative approach for bidirectional mode-locking of fiber lasers, as a potential source for intra-cavity phase interferometry. It consists of a passively driven active mechanism that both stabilizes the laser and controls the location of the crossing points of the counter-circulating pulses. For that purpose, the idea has been developed in both a theoretical and experimental level, with the design, construction, and testing of a fiber ring laser scheme capable of producing stable and independent (frequency unlocked) bidirectional pulses. In this manuscript, the description of the research is presented in seven separate chapters. The first chapter provides an overview of the project itself, the advantages of the controlling mechanism and the importance and practical applications of bidirectional mode-locked fiber lasers. Chapter two introduces the theoretical background necessary to understand pulse propagation in a nonlinear, birefringent, gain saturated optical fiber. In chapter three, the passive mechanism behind bidirectional mode-locking is detailed. Chapter four deals with the systems modeling and computer simulation, and chapter five explains the functional aspects of the self-regenerative system used to stabilize and control the laser pulsing. Chapter six describes the experimental setup itself, and presents the measured data results. Finally, chapter seven summarizes all the work done, emphasizing the consequences of the experimental findings, and laying out the foundations for future work.'
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