We present a numerical analysis of multi-mode pump absorption in recently proposed double-clad fiber with stadium-like cross section of the inner cladding and asymmetrically placed rare-earth doped core. Such a cross section allows easy splicing of the multi-mode pump fiber and single-mode signal fiber to the double-clad fiber. The full-vector finite element beam propagation method was used as a numerical tool. In order to allow excitation of the structure by arbitrary field profile, definite set of functionals satisfying unisolvence condition together with hybrid edge-nodal finite element basis was derived. The flat-top field profile and more realistic speckle pattern were considered in the analysis. The effect of coiling and simultaneous twisting of the fiber was taken into account. It was found that the twisting of the DC fiber significantly improves the pump absorption.
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The authors would like to acknowledge fruitful discussions and help from Valérie Doya from Laboratoire de Physique de la Matière Condensée, Université de Nice Sophia Antipolis and CNRS, France. This work was supported by the Academy of Sciences of the Czech Republic under the Grant M100671202, and in part by the Czech Science Foundation under Project No. 14-35256S.
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Koška, P., Peterka, P. Numerical analysis of pump propagation and absorption in specially tailored double-clad rare-earth doped fiber. Opt Quant Electron 47, 3181–3191 (2015). https://doi.org/10.1007/s11082-015-0194-2
- Double-clad fibers
- Finite element method
- Beam propagation method
- Fiber lasers