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Author: Bartelt, Hartmut Ă— End date: 2021 Ă— Start date: 2021 Ă— DDC: 530 Ă— Type: Text Ă— Version: publishedVersion Ă—

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    Intra-cavity measurement concept of dispersion properties with a tunable fiber-integrated laser
    (Philadelphia, Pa. : IOP Publ., 2019) Tiess, Tobias; Hartung, Alexander; Becker, Martin; Chojetzki, Christoph; Rothhardt, Manfred; Bartelt, Hartmut; Jäger, Matthias
    The dispersion properties of fibers depict a key characteristic to model the propagation of ultra-short pulses in waveguides. In the following, a new method is presented to directly measure the dispersion properties of fibers and optical components in the time domain. The analysis is based on pulse shape variations along the tuning range of a theta cavity fiber laser (TCFL) depending on the adjusted repetition rate. The automated measurement procedure, evaluating pulse symmetry, achieves a temporal sensitivity below 5 ps surpassing the resolution of the acquisition electronics. Exemplarily, two samples of Nufern PM980-XP fiber are investigated with an Yb-doped tunable TCFL retrieving the mean dispersion parameter D? by comparative measurements. The obtained results are compared to a reference method based on spectral interferometry. With deviations in D? between either approach of 0.3% and 1.3%, respectively, the results agree well within the measurement errors of the TCFL, verifying the presented concept. Due to the pulse formation process extending over multiple round trips, this approach achieves an enhanced sensitivity compared to competing direct temporal methods. Together with an alignment free operation, the fiber-integrated TCFL depicts a simple and robust concept showing potential in specific measurement scenarios such as in quality management. © 2019 Astro Ltd.
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    Plasma-based VAD process for multiply doped glass powders and high-performance fiber preforms with outstanding homogeneity
    (Hoboken, NJ : Wiley Interscience, 2020) Trautvetter, Tom; Schäfer, Jan; Benzine, Omar; Methling, Ralf; Baierl, Hardy; Reichel, Volker; Dellith, Jan; Köpp, Daniel; Hempel, Frank; Stankov, Marjan; Baeva, Margarita; Foest, RĂ¼diger; Wondraczek, Lothar; Wondraczek, Katrin; Bartelt, Hartmut
    An innovative approach using the vapor axial deposition (VAD), for the preparation of silica-based high-power fiber laser preforms, is described in this study. The VAD uses a plasma deposition system operating at atmospheric pressure, fed by a single, chemically adapted solution containing precursors of laser-active dopants (e.g., Yb2O3), glass-modifier species (e.g., Al2O3), and the silica matrix. The approach enables simultaneous doping with multiple optically active species and overcomes some of the current technological limitations encountered with well-established fiber preform technologies in terms of dopant distribution, doping levels, and achievable active core diameter. The deposition of co-doped silica with outstanding homogeneity is proven by Raman spectroscopy and electron probe microanalysis. Yb2O3 concentrations are realized up to 0.3 mol% in SiO2, with simultaneous doping of 3 mol% of Al2O3.