MW+ peak power sub-nsec 10-kHz repetition rate polarization-maintaining fiber-amplifiers using tapered Yb-doped fibers

Novel tapered Yb-doped polarization-maintaining (PM) large-mode-area (LMA) fibers were fabricated, with 25/250μm and 40/400μm core/clad at each end, and used in the last stage of a multi-stage Yb-fiber MOPA. The fiber-MOPA is controlled by high-speed FPGA for real-time control of the seed laser diode modulation, electro-optic modulator and acousto-optic modulator. Stable 0.3nsec pulses at 10kHz rate with 0.3mJ pulse energy (1MW peak power) is demonstrated. At 1nsec pulsewidth, scaling to >0.5mJ pulse energy is demonstrated. Polarization extinction ratio of 17dB is obtained with diffraction limited beam quality and excellent (<3%) power stability. Such compact and robust pulsed fiber amplifiers enable next generation of airborne and space lidar transmitters.