High power picosecond amplification in a large-core double-clad Yb-doped fiber

We report on the amplification of 21ps pulses up to 10W average output power in both a conventional ytterbium-doped large-core double-clad fiber and photonic crystal fiber (PCF). The picosecond fiber amplifier system consists of a mode-locked Nd:YVO4 oscillator and a diode-pumped double-clad large-core ytterbium-doped fiber. a passively mode-locked (SESAM) Nd:YVO4 oscillator is used as the picosecond seed source, which has repetition rate of 93 MHz, pulse duration as short as 19.2 ps at 1064 nm and an average power of 380 mW. At first, conventional double clad fiber is used as the amplifier medium, which has an inner cladding diameter of 250 mu m and the active core diameter of 30 mu m. The absorption coefficient of this fiber is as high as 9 dB/m at 976 nm. Secondly, PCF with an inner cladding diameter of 200 mu m, the active core diameter of 40 mu m is chosen for the amplifier with the same absorption coefficient as the conventional double clad fiber. For these two kinds of fiber amplifiers, both more than 10 W amplified output power have been achieved. Since lager mode area double clad ytterbium-doped fiber and photonic crystal fiber have been chosen in the amplifier, which would lead to a reduced nonlinearity, spectral broadening due to SPM is extensively suppressed.