50-W 2-μm Nanosecond All-Fiber-Based Thulium-Doped Fiber Amplifier

We report a two-stage 2-μm Tm³⁺ fiber amplifier seeded by an acousto-optic modulator (AOM) modulated narrow-bandwidth pulsed laser. Maximum output average power is over 50 W (slope efficiency of ~58%) at 50 kHz repetition rate, providing record performance in nanosecond 2-μm all-fiber-based amplifiers. The maximum pulse energy and peak power are ~1.0 mJ and 10 kW, respectively. The pulse width can be tuned from tens of to hundreds of nanosecond through changing the seed´s pump power or the modulation repetition rate. This high-power 2-μm Tm³⁺ fiber amplifier has an all-fiber-based configuration, providing high-degree stability and robustness. The laser emission wavelength, centered at ~1951 nm with a spectral width of ~1.4 nm, shows no obvious change with amplified power.