What the study found
The study finds that the inner cladding in a double-clad fiber changes both the optical and thermal mode structures, which alters the overlap between the fundamental mode (LP01, the main light pattern in the core) and higher-order modes. The authors report that this changes the effective strength of stimulated thermal Rayleigh scattering (STRS) and directly influences the predicted transverse mode instability (TMI) threshold.
Why the authors say this matters
The authors conclude that their formulation provides a quantitative and physically consistent tool for analyzing thermo-optic dynamics in Yb-doped double-clad fiber amplifiers. They say it supports the design of next-generation high-power fiber lasers with improved modal stability.
What the researchers tested
The researchers developed a coupled optical-thermal model for a continuous-wave, forward-pumped ytterbium-doped double-clad fiber amplifier operating at 976 nm pump wavelength and 1064 nm signal wavelength over an optimal length of 12 m. The model explicitly resolves the three radial regions of the double-clad fiber, uses the weakly guiding approximation in the core and a semi-weakly guiding approximation at the cladding interfaces, and calculates modal fields, transverse eigenvalues, thermal eigenmodes, gain saturation, and the STRS coupling coefficient.
What worked and what didn't
The approach captured higher-order mode penetration into the inner cladding and the transverse eigenvalues relevant to TMI. The results show that the inner cladding modifies the optical and thermal mode structures and changes the effective STRS strength, but the abstract does not provide a numerical threshold value or a direct comparison with an experiment.
What to keep in mind
The abstract does not describe experimental validation or give quantitative performance numbers. It also does not state any limitations beyond the modeling scope, and the conclusions are limited to the continuous-wave, forward-pumped Yb-doped double-clad fiber amplifier case studied here.
Key points
- The inner cladding changes optical and thermal mode structures in the modeled fiber amplifier.
- Those changes alter the overlap between LP01 and higher-order modes.
- The altered overlap changes the effective strength of stimulated thermal Rayleigh scattering (STRS).
- The model predicts that STRS affects the transverse mode instability threshold.
- The abstract does not report experimental validation or numerical threshold values.
Disclosure
- Research title:
- Inner cladding alters predicted TMI threshold in fiber amplifiers
- Authors:
- Elbis Santos Cardoso, Ricardo Elgul Samad, Cláudio C. Motta
- Institutions:
- Universidade Federal de São Paulo, National Nuclear Energy Commission
- Publication date:
- 2026-03-05
- OpenAlex record:
- View
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