22 February 2017 Power scaling of a hybrid microstructured Yb-doped fiber amplifier
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Abstract
Hybrid microstructured fibers, utilizing both air holes and high index cladding structures, provide important advantages over conventional fiber including robust fundamental mode operation with large core diameters (>30μm) and spectral filtering (i.e. amplified spontaneous emission and Raman suppression). This work investigates the capabilities of a hybrid fiber designed to suppress stimulated Brillouin scattering (SBS) and modal instability (MI) by characterizing these effects in a counter-pumped amplifier configuration as well as interrogating SBS using a pump-probe Brillouin gain spectrum (BGS) diagnostic suite. The fiber has a 35 μm annularly gain tailored core, the center doped with Yb and the second annulus comprised of un-doped fused silica, designed to optimize gain in the fundamental mode while limiting gain to higher order modes. A narrow-linewidth seed was amplified to an MI-limited 820 W, with near-diffraction-limited beam quality, an effective linewidth ~ 1 GHz, and a pump conversion efficiency of 78%. Via a BGS pump-probe measurement system a high resolution spectra and corresponding gain coefficient were obtained. The primary gain peak, corresponding to the Yb doped region of the core, occurred at 15.9 GHz and had a gain coefficient of 1.92×10-11 m/W. A much weaker BGS response, due to the pure silica annulus, occurred at 16.3 GHz. This result demonstrates the feasibility of power scaling hybrid microstructured fiber amplifiers
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Cody Mart, Benjamin Pulford, Benjamin Ward, Iyad Dajani, Thomas Ehrenreich, Brian Anderson, Khanh Kieu, Tony Sanchez, "Power scaling of a hybrid microstructured Yb-doped fiber amplifier", Proc. SPIE 10083, Fiber Lasers XIV: Technology and Systems, 100830X (22 February 2017); doi: 10.1117/12.2249863; https://doi.org/10.1117/12.2249863
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