Fabrication of microlenses on ytterbium-doped double-cladding microstructured optical fibers with a CO2 laser for effective optical coupling
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Due to the air holes in cladding, it is difficult to process for end faces of ytterbium-doped double-cladding microstructured optical fibers. In this paper, we demonstrate the fabricating method of microlenses on ytterbium-doped double-cladding microstructured optical fibers with a CO2 laser to enhance the coupling efficiency. The theoretical and experimental investigation is carried out to study the effect of minor axis semidiameter and major axis semidiameter of ellipsoidal microlenses on coupling efficiency. The coupling efficiency is up to 88%, which is 14.6% higher than that of the perpendicular flat-end microstructured optical fiber using a free space optical path. These results suggest that the proposed end face processing on microstructured optical fibers provides a straightforward solution for the production of microlenses for laser coupling applications in high-power fiber lasers.
KeywordsMicrostructured optical fibers Ytterbium-doped CO2 laser Ellipsoidal microlenses Optical coupling
The authors acknowledge Guangdong Province Key Laboratory of Nano-photonic Functional Materials and Devices for experimental components and Xian Wang for help with the experiments. And the authors are also grateful to National Natural Science Foundation of China (NSFC) (61575066, 61527822, 61735005), Guangdong Natural Science Foundation (2017A030313333), Science and Technology Program of Guangzhou (201707010133), Science and Technology Planning Project of Guangdong Province (2017KZ010201), National Key Research and Development Program of China (2018YFB0407400) and GDUPS (2017).
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