160 W average power single-polarization, nanosecond pulses generation from diode-seeded thulium-doped all-fiber MOPA system

摘要

We demonstrate high average power all-fiber single-polarization thulium(Tm)-doped nanosecond laser based on all-fiber master-oscillator power-amplifier (MOPA).The seed source employed is a directly modulated discrete-mode (DM) diode at 2 μm with pulse width of 15.8 ns and tunable repetition rate range of 400 kHz to 4 MHz. The pulse duration reduced to 6 ns as the gain reshaping during amplification. The MOPA yields 160 W maximum average powers at 4 MHz repetition with 6 ns pulse width, with respect to pulse energy of 40 μJ and peak-power of 6.7 kW. The slope efficiency for the last stage of PM LMA Tm-doped fiber amplifier was 48.8% with respect to launched pump power. The polarization extinction ratio (PER) of system measured at maximum output power is beyond 15 dB. The beam quality factor M~2 was measured to be 1.5 at average output power of 160 W. To the best of our knowledge, this is the highest average power 2 μm nanosecond pulses laser from laser diode seeded all-fiber MOPA systems to date.