Broad-band diode-pumped ytterbium-doped fiber amplifier with 34-dBm outputpower

We investigate a high-power diode-pumped double-clad ytterbium-doped fiber amplifier with 34-dBm average output power and 1050-1095-nm bandwidth. A mu ltidiode concentrator pumps the amplifier at 980 nm, with similar to 6 W Of power launched into the inner cladding. Besides CW-signals, we amplify pul ses from a mode-locked laser to 1 kW of peak power with only minor nonlinea r distortions as well as pulses from a Q-switched laser to 50 mu J of energ y. Reflections and backscatter limit the gain of the amplifier to 40 dB for a pump power of 2.5 W, For higher pump-powers than this, the amplifier sta rted to self-Q-switch, The results are important for the development of cla dding-pumped high-power fiber amplifiers.