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Proceedings Paper

Modeling of intermodal couplings in large-mode area Yb-doped double-cladding fibers applied in continuous-wave high power fiber lasers
Author(s): Weixuan Lin; Martin Rochette
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Paper Abstract

Nonlinear effects are well-known to limit the power scalability of continuous-wave (CW) high power fiber lasers (HPFL). In addition to nonlinear effects than act over the fundamental mode, intermodal nonlinear effects are currently drawing the interest of researchers. Specifically, intermodal nonlinear effects in CW-HPFLs such as degenerate intermodal four-wave mixing (IM-FWM) and stimulated Raman scattering(SRS)-induced intermodal wave-mixing (IM-WM) have been investigated recently; the former generates Stokes and idler at different modes, and the latter transfers power from the fundamental mode to the Raman shifted high-order modes. Here, we report a model that encompasses the aforementioned intermodal couplings in CW-HPFLs and simulate them. More specifically, a model based on multimode generalized nonlinear Schrodinger equations is developed and used to simulate the intermodal couplings in 25/400μm Yb-doped large-mode area fiber amplifiers. Based on the phase-matching condition of IM-FWM, the relation between degenerate IM-FWM frequency shift, modal group velocities, and modal group velocity dispersions is found and applied in the model. By using this model, degenerate IM-FWM and SRS-induced IM-WM, which are intermodal phenomena recently discussed in literatures of CW-HPFLs, are successfully simulated. In addition, a novel intermodal phenomenon is found and discussed, which is the high-order mode second-ordered Stokes resulting from the joint effect of degenerate IM-FWM and SRS-induced intermodal wave-mixing (IM-WM). To the best of our knowledge, this model is the first to include degenerate IM-FWM in the context of CW-HPFLs and reveal the joint effect of the aforementioned intermodal couplings. The result also gives insight of the conditions leading to intermodal couplings.

Paper Details

Date Published: 2 March 2020
PDF: 10 pages
Proc. SPIE 11264, Nonlinear Frequency Generation and Conversion: Materials and Devices XIX, 1126420 (2 March 2020); doi: 10.1117/12.2539348
Show Author Affiliations
Weixuan Lin, McGill Univ. (Canada)
Martin Rochette, McGill Univ. (Canada)

Published in SPIE Proceedings Vol. 11264:
Nonlinear Frequency Generation and Conversion: Materials and Devices XIX
Peter G. Schunemann; Kenneth L. Schepler, Editor(s)

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