High-Power Highly Linear-Polarized Nanosecond All-Fiber MOPA at 2040 nm

Abstract

We demonstrate a nanosecond all-fiber MOPA with linear-polarized output at 2040 nm, seeded by an in-bandpumped gain-switched thulium-doped fiber laser, which can directly output tens-of-microjoules pulses with designable pulse duration and Gaussian-like pulse profile. After only two stages of amplification, we achieve an average power of 70 W at a pulse width of 114 ns and a repetition rate of 10 kHz, corresponding to a pulse energy of 7 mJ and a peak power of 53.8 kW. Benefit from the on-site polarization control technique we proposed, a polarization extinction ratio (PER) of 25 dB at the highest output is also obtained. To the best of our knowledge, this is the highest power nanosecond all-fiber laser reported at 2-µm waveband and the PER is also a record among high-power fiber lasers.

A monolithic 2042nm hybrid pumped gain-switched thulium-doped fiber laser

“…Most pump pulse energy was consumed before reaching the lasing threshold; only a small part of pump energy was used to trigger the population inversion and lasing 2μm band pulse. The output power drops to 0.47W at 40kHz [7] and 0.17W at 10kHz [8].…”

Cascade-Gain-Switching for Generating 3.5-$\mu$m Nanosecond Pulses From Monolithic Fiber Lasers

“…Compared with the lasing process having the relaxation from pump absorption to laser radiation, the in-band pumping has instinct advantages on pulse regulation [11]. This technique has been established for 10 years [12] and used in many applications such as mid-infrared optical parametric oscillator [13], mid-infrared supercontinuum generation [14], and high-power fiber amplification [15], [16]. In our previous publication [17], the theoretical model of this kind of lasers has been described in very detail, so we will not repeat it here.…”