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Improvement of the manufacturing process chain of sintered active XLMA fibers and their preforms for use in high power, high efficiency fiber resonators

: Langner, A.; Moser, F.; Plass, J.; Schönfeld, D.; Schötz, G.; Brabant, T.; Kuka, G.; Giesberts, M.; Baer, P.; Klein, S.; Fitzau, O.; Hoffmann, H.D.; Rehmann, G.; Krause, V.


Carter, A.L. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Fiber Lasers XVI: Technology and Systems : 4-7 February 2019, San Francisco, California, United States
Bellingham, WA: SPIE, 2019 (Proceedings of SPIE 10897)
ISBN: 978-1-5106-2437-5
ISBN: 978-1-5106-2436-8
Art. 108970F, 13 pp.
Conference "Fiber Lasers - Technology and Systems <16, 2019, San Francisco/Calif.>
Industrial Laser, Laser Source and Laser Applications Conference (LASE) <2019, San Francisco/Calif.>
Photonics West Conference <2019, San Francisco/Calif.>
Conference Paper
Fraunhofer ILT ()

In this paper, we present our current work towards a highly efficient XLMA (extra-large mode area) fiber-based laser, which is being performed in the EKOLAS consortium within the BMBF-funded EffiLAS (efficient high-performance laser beam sources) research alliance. To this end, the complete manufacturing process chain of the XLMA fiber was reviewed and optimized. The work started with the material composition of the active XLMA preform with the goal of improving the purity and thus the background loss. A successfully implemented fluorine co-doping process allows refractive index adjustment of the active core material which improves the beam quality of the laser fibers without changing the concentration of active ions in the glass composition. The preform is subjected to a screening in which possible scatter centers, e.g. bubbles, inclusions or contaminants, are mapped and categorized, in order to identify defects, which could lead to a failure in the drawn fiber, already at an early production stage. The subsequent fiber drawing is monitored for scattering using the emissions from the heated preform as well as for inhomogeneities of the dopants using a phase measurement technique. Finally, the fiber is tested for residual impurities and background losses using a multi-mode OTDR to ensure that the fibers are free of any defects.