We report a 120 W high average power all-fiber subnanosecond master oscillator power amplifier (MOPA) system with a two-stage amplifier chain. The seed source is an ytterbiumdoped single mode fiber laser passively mode-locked by nonlinear polarization rotation (NPR). Its pulse width is tunable from 0.59 ns to 1.2 ns by changing the length of the laser cavity. The average output power of 91.5 mW is obtained at 26.3 MHz with pulse width of 0.59 ns. A large mode area double cladding high-absorption ytterbium-doped fiber is introduced into the master power amplifier to suppress the nonlinear effects. Finally, 120 W average output power is obtained with single pulse energy of 4.56 μJ, and its optical-to-optical conversion efficiency is up to 83.9%. In addition, we demonstrate 19.5 W average-power supercontinuum generation in photonic crystal fiber (PCF) using this subnanosecond pulsed fiber amplifier.
We report a picosecond ytterbium-doped double-clad fiber amplifier with a semiconductor saturable absorber mirror (SESAM) mode locking large mode area photonic crystal fiber (PCF) oscillator as the seed source. In the seed source, without any dispersion compensator or tunable elements in the cavity, we obtain self-starting mode locking of a tunable ytterbium-doped fiber oscillator. The 1037-1054 nm tuning range is achieved by proper adjustment of the half-wave plate and SESAM in the laser cavity. More than 1 W output power at the different wavelengths of operation has been achieved in experiments. For the fiber amplifier seeded with an SESAM mode locking PCF fiber oscillator, an average output power of 21 W has been demonstrated at a repetition rate of 45.9 MHz with a pulse duration of 8.8 ps, corresponding to a pulse energy of 458 nJ and a peak power of 52 kW. The nonlinear effect of self-phase-modulation (SPM), which results in spectral broadening, has been observed during the amplified experiments.
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