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9 June 2014 50μm-core Yb-doped leakage channel fiber with flattened mode
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Power scaling of fiber lasers is highly desirable in many applications but is mainly limited by nonlinear effects. Large-mode-area fibers have been used to mitigate this limit, such as the leakage channel fiber (LCF). The mode intensity profile in these fibers typically exhibits Gaussian-like structure with much reduced effective mode-area compared to the physical fiber core area. Thus, a flat-top mode with a uniform intensity distribution is more suitable for larger effective mode-area without having to increase core size. In this work, we demonstrate the first flat-top mode generated in a 50 μm-core Yb-doped LCF fiber. The mode flattening from Gaussian beam to a flat-top one is achieved by using a 30 μm uniform Yb-doped area in the core center with a refractive index very slightly below that of the background silica glass by 2×10-4. The resulting flat-top mode has a significantly increased effective mode area of ~1880 um2, which is ~50% larger than that of a conventional uniform core and ~6 times the effective mode area of the flat-top mode record demonstrated previously. A 6m-long fiber is also tested in a laser configuration with a slope efficiency of ~84% at 1026 nm with respect to the absorbed pump power at 976 nm.
© (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Fanting Kong, Guancheng Gu, Thomas W. Hawkins, Joshua Parsons, Maxwell Jones, Christopher Dunn, Monica T. Kalichevsky-Dong, Kanxian Wei, Bryce Samson, and Liang Dong "50μm-core Yb-doped leakage channel fiber with flattened mode", Proc. SPIE 9081, Laser Technology for Defense and Security X, 90810F (9 June 2014);

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