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CW and pulsed performance of Tm-doped photonic crystal fiber lasers

We demonstrate single-mode, highly polarized output from a thulium-doped photonic crystal fiber (PCF) with 50 μm core diameter and an ultra-large mode area >1000 μm2. To our knowledge, this is the largest mode area of any flexible PCF and is capable of enabling the generation of high peak powers. In a Q-switched oscillator configuration, this fiber produces peak powers as high as 8.9 kW with 435 μJ, 49 ns pulses, >15 dB polarization extinction ratio and quasi diffraction-limited beam quality. The pulse energy was scaled to >1 mJ in amplifier configuration.