High-peak-power (>1.2 MW) pulsed fiber amplifier

We report results from Yb-doped fiber amplifiers seeded with two microchip lasers having 0.38-ns and 2.3ns pulse durations. The shorter duration seed resulted in output pulses with a peak power of > 1.2 MW and pulse energy of 0.67 mJ. Peak power was limited by nonlinear processes that caused breakup and broadening of the pulse envelope as the pump power increased. The 2.3-ns duration seed laser resulted in output pulses with a peak power of > 300 kW and pulse energy of > 1. 1 mJ. Pulse energies were limited by the onset of stimulated Brillouin scattering and ultimately by internal optical damage (fluences in excess of 400 J/cm(2) were generated). In both experiments, nearly diffraction-limited beam profiles were obtained, with M-2 values of < 1.2. Preliminary results of a pulse-amplification model are in excellent agreement with the experimental results of the amplifiers operating in the low-to-moderate gain-depletion regime.