Record peak power single-frequency erbium-doped fiber amplifiers

In this work we present results on the amplification of narrow-linewidth nanosecond pulses in a recently developed ytterbium-free erbium-doped large mode area fiber cladding pumped at 980 nm. At first, a co-propagating all-fiber amplifier scheme was used. Using 1 m of active fiber length in such configuration a peak power of 4 kW limited by instabilities caused by stimulated Brillouin scattering (SBS) was achieved. To the best of our knowledge this is the highest peak power ever reported for single-frequency single-mode silica-based fiber sources near 1550 nm. Then all-fiber counter-pumped configuration with 6 m of active fiber was used and peak power of 900 W was obtained. In this case peak power was limited by SBS generation in a passive fiber at the laser output. Slope electrical-to-optical conversion efficiency of 8 % demonstrated in such scheme is a record value for kW-level single-mode single-frequency Er-doped nanosecond fiber lasers.