Enhanced pump absorption efficiency in coiled and twisted double-clad fibers for fiber lasers

0519192 - ÚFE 2020 RIV PL eng C - Conference Paper (international conference)
Peterka, Pavel - Koška, Pavel - Jasim, Ali - Kanagaraj, Nithyanandan - Aubrecht, Jan - Kamrádek, Michal - Podrazký, Ondřej - Todorov, Filip - Kašík, Ivan - Honzátko, Pavel
Enhanced pump absorption efficiency in coiled and twisted double-clad fibers for fiber lasers.
21st International Conference on Transparent Optical Networks, ICTON 2019. Varšava: IEEE, 2019 - (Jaworski, M.; Marciniak, M.), č. článku Th.B6.1. ISBN 978-1-7281-2779-8. ISSN 2162-7339. E-ISSN 2161-2064.
[21st International Conference on Transparent Optical Networks, ICTON 2019. Angers (FR), 09.07.2019-13.07.2019]
R&D Projects: GA ČR(CZ) GA19-03141S
Institutional support: RVO:67985882
Keywords : Optical pumping * Rare-earth-doped fibers * Thulium-doped fibers
OECD category: Optics (including laser optics and quantum optics)

High-power operation of fiber lasers was mainly enabled by the invention of cladding-pumping in a double-clad fiber structure. Pump absorption is enhanced by broken circular symmetry of inner cladding cross-sections and by mode-scrambling of the pump modes resulting from unconventional fiber coiling. However, theoretical studies were limited to the assumption of a straight fiber until recently, when the rigorous model accounting for double-clad fiber bending and twisting was described. It was found that squeezing of the effective area of the pump radiation due to fiber bending plays an important role in cladding-pump absorption enhancement. We review results of numerical modeling of pump absorption in various types of double-clad fibers, e.g., with cross-section shape of hexagon, stadium, and circle, two-fiber bundle (so-called GTWave fiber structure) a panda fibers are also analyzed. The presented results can have a practical application and potential impact in the construction of fiber lasers: with pump absorption efficiency optimized by our new model (the other models did not take into account fiber twist), the double-clad fiber of shorter length can be used in the fiber lasers and amplifiers. This dramatically minimizes the deleterious effect of background losses and nonlinear effects
Permanent Link: http://hdl.handle.net/11104/0304216