Abstract
We describe in detail a high energy, high power ultrafast thulium-doped fiber laser system. The pulse energy of 156 μJ was realized. The laser system is comprised of a mode-locked 2020-nm seed oscillator and multiple-stage power/energy amplifiers. The seed oscillator output pulses at a repetition rate of 2.5 MHz. The seed pulses were stretched with the anomalous dispersion fiber to the duration of 320 ps. An acousto-optic modulator was used as a pulse picker to lower the repetition rate. A two-stage preamplifier was used to boost the pulse energy to 3 μJ. The pulse energies of up to 156 μJ and the average power of 15.6 W were obtained from the final stage of power amplifier at a repetition rate of 100 kHz with a slope efficiency of 26%. The pulse durations of 780 fs were obtained after pulse compression. High optical signal-to-noise ratio (OSNR) and low background noise were also achieved at this low repetition rate.
Highlights
High-energy short pulses emission at an eye-safer wavelength of 2-μm region are desirable for many applications such as laser sensing, free space optical communications, midinfrared (IR) spectroscopy, material processing, laserinduced breakdown spectroscopy, midIR supercontinuum generation, IR countermeasures, and efficient high harmonic X-ray generation.[1,2,3,4,5,6,7,8]
In our previous work,[15,16] we demonstrated a high energy master oscillator power amplifier (MOPA) based on the mode-locked Tm-doped fiber laser oscillator and a twostage fiber amplifier at a wavelength of 2 μm with chirped pulse amplification
It is composed of a 2020 nm Tm-doped fiber laser seed oscillator, a fiber stretcher, a two-stage fiber power amplifier, an acousto-optic modulator (AOM), and a final stage high-energy amplifier
Summary
High-energy short pulses emission at an eye-safer wavelength of 2-μm region are desirable for many applications such as laser sensing, free space optical communications, midinfrared (IR) spectroscopy, material processing, laserinduced breakdown spectroscopy, midIR supercontinuum generation, IR countermeasures, and efficient high harmonic X-ray generation.[1,2,3,4,5,6,7,8] Thulium (Tm)-doped short-pulse fiber lasers are of particular interest for such applications because they offer the potential for compact and robust construction. Tm-doped femtosecond fiber lasers had been demonstrated in several mode-locking schemes such as nonlinear polarization rotation, carbon nanotube, graphene oxide, and semiconductor saturable absorbing mirrors.[9,10,11,12,13] the output pulse repetition rates from these oscillators were usually from a few tens of megahertz to over 100 MHz. Laser pulse trains at such high repetition rates were not convenient to achieve high pulse energy in amplification stage. The seed laser generated a pulse train at a repetition rate of 2.5 MHz and the two-stage fiber amplifier boosted the pulse energy to 54 μJ with a compressed pulse width of 910 fs. A sequence of mode locking pulse train was directly generated in a Tm-doped fiber seed oscillator at the central wavelength of 2020 nm. The pulse width of 780 fs was obtained
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