Abstract

A novel approach to achieving robust single-spatial-mode operation of cladding-pumped fiber lasers with multimode cores is reported. The approach is based on the use of a fiber geometry in which the core has a helical trajectory within the inner cladding to suppress laser oscillation on higher-order modes. In a preliminary proof-of-principle study, efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser with a $30\mu \mathrm{m}$ diameter core and a numerical aperture of 0.087 has been demonstrated. The laser yielded $60.4\mathrm{W}$ of output at $1043\mathrm{nm}$ in a beam with $M^2<1.4$ for $92.6\mathrm{W}$ launched pump power from a diode stack at $976\mathrm{nm}$. The slope efficiency at pump powers well above threshold was $\sim 84\%$, which compares favorably with the slope efficiencies achievable with conventional straight-core Yb-doped double-clad fiber lasers.

© 2006 Optical Society of America

75 W 40% efficiency single-mode all-fiber erbium-doped laser cladding pumped at 976 nm

L. V. Kotov, M. E. Likhachev, M. M. Bubnov, O. I. Medvedkov, M. V. Yashkov, A. N. Guryanov, J. Lhermite, S. Février, and E. Cormier
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Highly efficient in-band pumped Er:YAG laser with 60 W of output at 1645 nm

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