Abstract
We report a gain-switched diode-seeded thulium doped fiber master oscillator power amplifier (MOPA) producing up to 295-kW picosecond pulses (35 ps) at a repetition rate of 1 MHz with a good beam quality (M2 ~1.3). A narrow-band, grating-based filter was incorporated within the amplifier chain to restrict the accumulation of nonlinear spectral broadening and counter-pumping of a short length of large-mode-area (LMA) fiber was used in the final stage amplifier to further reduce nonlinear effects. Finally, we generated watt-level >2.5-octave supercontinuum spanning from 750 nm to 5000 nm by using the MOPA output to pump an indium fluoride fiber.
Highlights
Thulium doped fiber lasers (TDFLs) have experienced rapid development in the past few years, driven by a diverse range of applications including gas sensing, laser processing of both polymers and biological tissues, and nonlinear frequency conversion [1,2,3,4,5]
We report a gain-switched diode-seeded thulium doped fiber master oscillator power amplifier (MOPA) producing up to 295-kW picosecond pulses (35 ps) at a repetition rate of 1 MHz with a good beam quality (M2 ~1.3)
Funding EPSRC AirGuide Photonics Programme Grant (Grant EP/P030181/1) Acknowledgment The authors acknowledge Dr Peter Shardlow from ORC for providing the in-house fabricated thulium doped fibers
Summary
Thulium doped fiber lasers (TDFLs) have experienced rapid development in the past few years, driven by a diverse range of applications including gas sensing, laser processing of both polymers and biological tissues, and nonlinear frequency conversion [1,2,3,4,5]. Wang et al recently presented a nanosecond-pulsed thulium-doped LMA-fiber MOPA system with an average output power scalable from 150 W to 238 W [9]. Stutzki et al reported femtosecond pulses with a peak power in excess of 200 MW from a CPA system based on a LMA thulium doped fiber with 25-μm core diameter and a thulium-doped large-pitch rod fiber with a mode field diameter of 65 μm, respectively [14,15]. High-power picosecond lasers can be a good option for many nonlinear frequency conversion applications due to the simpler system architectures compared to femtosecond CPA systems and much shorter pulse duration in comparison to nanosecond lasers [16]. Careful management of fiber nonlinearity and signal purity are essential to accomplish further power scaling from thulium-doped fiber MOPA systems
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