Nonlinear Pulse Dynamics in Fiber Lasers at the Verge of Mode-Locking and in Transition Regimes

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Title: Nonlinear Pulse Dynamics of Ultrafast Fiber Lasers in Transition Regimes Non-technical description: Lasers with ultrashort pulse durations have found widespread applications in precision measurements, micromachining, biomedical imaging and medical surgery. For any of these fields, it is crucial to be able to monitor and predict the power and laser properties to avoid excessive tissue or material damage. As these lasers feature extremely short pulse durations (on the order of femtoseconds) which exceed the fastest electronic characterization instruments, an existing challenge is to capture the pulse-to-pulse evolution in real-time. The goal of this proposal is to develop new real-time optical characterization methods that can provide insight into the pulse-by-pulse behavior and characterize novel lasers states. These methods can enable new modulation schemes in communication systems while having fundamental impact on laser development and optimization. In addition, the proposed real-time characterization methods can provide powerful analysis tools for continuous monitoring of cell mechanisms, fluid dynamics or chemical reaction kinetics. This project also provides an opportunity to train undergraduate and graduate students at the intersection of laser physics, systems engineering, materials science, and real-time characterization to build a new generation of multi-faceted researchers to tackle the interdisciplinary nature of technological and societal challenges in the future. The PI will organize professional networking and mentoring opportunities through a Boston-wide Photonics Networking series that highlights female engineers. This aims to bring together a diverse group of engineers and scientists and to encourage underrepresented minorities in the field. Technical description: The PI proposes to develop a real-time measurement system to analyze the pulse-to-pulse evolution simultaneously with phase coherence in thulium-holmium doped fiber lasers around 2 micron wavelengths as well as for erbium doped fiber lasers in 1.5 micron region. The proposal aims at exploring and characterizing transient effects, rapid fluctuations and nonlinear pulse dynamics on a pulse-by-pulse basis for ultrafast fiber lasers, e.g. at the verge of mode-locking. A modified time-stretching technique based on dispersive Fourier transform is to be developed to capture pulse behavior on a single pulse scale. Systematic studies aimed at resolving the intricate interplay between different pulse shaping mechanisms in fibers will lead to fundamental insights into pulse dynamics and transient states that can be applied to design novel laser cavities, resolve polarization evolution and optimize performance parameters.