1 Department of Photonics Engineering, Technical University of Denmark2 Fiber Sensors and Supercontinuum Generation, Department of Photonics Engineering, Technical University of Denmark3 Risø National Laboratory for Sustainable Energy, Technical University of Denmark4 Department of Mechanical Engineering, Technical University of Denmark5 NKT Photonics A/S
The extreme broadening phenomenon of supercontinuum (SC) generation in optical fibers is the basis of SC laser sources. These sources have numerous applications in areas, such as spectroscopy and microscopy due to the unique combination of extremely broad spectral bandwidths, high spectral power densities, and high spatial coherence. In this work the feasibility of applying gain-switched all-fiber lasers to SC generation is investigated. It is motivated by the simplicity of the architecture and the ability to scale the optical output power of such fiber lasers. The physics of fiber lasers are reviewed to understand the mechanisms involved in gain-switching. A detailed numerical model is provided to give deep insight into the different stages of pulse generation. A simplied model is also developed to derive an analytic expression for the pulse duration. Extensive experiments with gain-switching of fiber lasers with a variety of different configurations are carried out. The peak power, pulse duration, bandwidth, and scaling with repetition rate are thoroughly described. General guidelines are submitted to enable designing of gainswitched fiber lasers with specifically tailored properties. The physics of SC generation are reviewed with focus on the quasicontinuous wave pumping regime. Experiments with a gain-switched ber laser as a pump for SC generation in photonic crystal fibers are carried out. Requirements for effcient SC generation are analyzed. Finally, an optimization of photonic crystal fibers for gain-switched fiber laser-pumped SC generation is presented.
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Bang, Ole, Mattsson, Kent Erik, Skovgaard, Peter M. W., Hansen, Kim P.