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Peak power scaling in Tm doped fiber lasers to MW-level

In this manuscript we present our recent achievements utilizing thulium-doped photonic crystal fiber rods (PCF-rods) for lasing at 2 μm wavelength and their potential as high peak power amplifiers. Two PCF-rods with 65 μm and 80 μm core diameter were first separately characterized in CW laser oscillators. The rods were pumped with a 793 nm laser diode and produced more than 18 W output power with near diffraction limited beam quality and a slope efficiency of up to 27.8 %. Implementing an intracavity high reflectivity grating for lasing wavelength selection enabled a tuning range of 180 nm from 1810 nm to 1990 nm. Thereafter the PCF-rod with 80 μm core was used as an amplifier and produced similar output powers when seeded with up to 4 W at 1960 nm from a master oscillator power amplifier (MOPA). The slope efficiency in this case was reduced to 20.1 % mainly due to the center wavelength of 1960nm. We are in the process of characterizing these rods in a pulsed amplification configuration to surpass MW-level peak power with multi-mJ pulse energy.