High-peak-power pulse amplification using Yb-doped double-clad fiber

A high peak-power, high repetition rate Master Oscillator Power Amplifier (MOPA) system incorporating an Yb-doped fiber amplifier and its second harmonic generation were investigated in detail. The oscillator is actively Q-switch microchip laser at repetition rate of 50 kHz with a pulse width of 2.8ns. The amplifier employing Yb-doped polarization maintaining fiber, having a large mode area was exited by a laser diode with an optical power of 17W. As results, the amplified average output power of 10W and the optical conversion efficiency of 59% were achieved. In this MOPA system, second harmonic generation (SHG) experiments were performed using KTP and LBO crystals. The conversion efficiency of 21% and 40%, the maximum SHG power of 0.92 W and 3.3W were obtained for KTP crystal and LBO crystal respectively.