Tradeoff Between the Brillouin and Transverse Mode Instabilities in Yb-doped Fiber Amplifiers
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Author/Creator
Author/Creator ORCID
Date
2022-10-19
Type of Work
Department
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Citation of Original Publication
J. T. Young, A. J. Goers, D. M. Brown, M. L. Dennis, K. Lehr, C. Wei, C. R. Menyuk, and J. Hu, "Tradeoff between the Brillouin and transverse mode instabilities in Yb-doped fiber amplifiers," Opt. Express 30, 40691-40703 (2022). https://doi.org/10.1364/OE.472829
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© 2022 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.
Subjects
Abstract
The Brillouin instability (BI) due to stimulated Brillouin scattering (SBS) and the transverse
(thermal) mode instability (TMI) due to stimulated thermal Rayleigh scattering (STRS) limit
the achievable power in high-power lasers and amplifiers. The pump power threshold for BI
increases as the core diameter increases, but the threshold for TMI may decrease as the core
diameter increases. In this paper, we use a multi-time-scale approach to simultaneously model
BI and TMI, which gives us the ability to find the fiber diameter with the highest power threshold.
We formulate the equations to compare the thresholds of the combined and individual TMI and
BI models. At the pump power threshold, and below there is a negligible difference between
the full and individual models, as BI and TMI are not strong enough to interact with each other.
The highest pump threshold occurs at the optimal core size of 43 휇m for the simple double-clad
geometry that we considered. We found that both effects contribute equally to the threshold, and
the full BI and TMI model yields a similar threshold as the BI or TMI model alone. However,
once the reflectivity is sufficiently large, we find in the full BI and TMI model that BI may trigger
TMI and reduce the TMI threshold to a value lower than is predicted in simulations with TMI
alone. This result cannot be predicted by models that consider BI and TMI separately. Our
approach can be extended to more complex geometries and used for their optimization