20-W Wavelength-Tunable Picosecond Yb-Doped Fiber MOPA Source Seeded by an NPR Mode-Locked Fiber Laser

We demonstrated a high-power wavelength-tunable picosecond Yb-doped fiber master oscillator power amplifier source without any tunable elements for the first time. This wavelength-tunable output was realized based on the birefringence-induced filter effect of the nonlinear polarization rotation mode-locked fiber laser, which worked as the seed source. Through cascaded single-mode Yb-doped fiber preamplifiers together with two double-cladding Yb-doped fiber amplifiers, the pulses were amplified up to 21.2-W output power in the wavelength range from 1038.4 to 1060 nm with a pulse duration of 9.5 ps, an optical signal-to-noise ratio of 25 dB, and a beam quality M² of 1.16 at the repetition rate of 178 MHz.