High-power, single-mode, linearly polarized, ytterbium-doped fiber superfluorescent source.

High-power operation of a single-mode, linearly polarized, broadband superfluorescent fiber source has been achieved by using a two-stage cladding-pumped fiber configuration comprising a low power, single-ended, ytterbium-doped superfluorescent fiber seed source and a high-power cladding-pumped, polarization-maintaining, large-mode-area, ytterbium-doped amplifier pumped by a high-power diode source at 976 nm. The source yielded a maximum linearly polarized output of 106 W with a slope efficiency of up to 67% with respect to the launched pump power and with a measured polarization extinction ratio of 13.5 dB. The wavelength spectrum of the superfluorescent source spanned the range continuously from ~1035 to 1100 nm, and the bandwidth (FWHM) of the emission spectrum was 21 nm. The minimum seed power required for an output power over 100 W was only 10 mW, corresponding to an effective power gain in the amplifier stage of 40 dB. Single-spatial-mode operation with a beam propagation factor (M(2))<1.1 was achieved by bending the amplifier fiber to a bend radius of ~8 cm, without a significant reduction in output power.