In this work, a high-power all-fiber mid-infrared (MIR) supercontinuum (SC) laser source was generated in a short piece of centimeter level germania-doped fiber (GDF). The MIR SC generation in GDF was pumped by a 2 μm chirped pulse amplification (CPA) system. The seed source was a passively mode-locked oscillator by semiconductor saturable absorber mirror (SESAM) with a pulse width of 29.7 ps, a spectrum width of 0.3 nm and a fundamental repetition rate of 44.31 MHz. A high-power pump source with a spectral coverage of 1.9~2.2 μm was obtained in thulium-doped fiber amplifier (TDFA). Adopted by 19 cm-long 64 mol. % GDF, we obtained a broadband SC source spanning from 1850 to 3000 nm. The generated SC had a maximum output power of 31.2W with a pump slope efficiency from 56.2% to 30.9%. By optimizing fusion-spliced parameters, a high optical coupling efficiency was obtained between single-mode fiber (SMF) and GDF. In addition, we measured the pulse characteristics of SC laser source in different peak power of pumping source and different length of GDF. It paved the way for further realization of high power and wide spectrum MIR SC laser source.
In this letter, we report a high-power all-fiber mid-infrared (MIR) supercontinuum (SC) laser source based on a short piece of centimeter level germania-core fiber (GCF). The pump source at the wavelength of 2 μm was directly generated from a single-mode fiber laser. The all-fiber seed oscillator was passively mode-locked by a SESAM to generate pulse duration of 62 ps at a fundamental repetition rate of 44.31 MHz in a linear cavity. After all-fiber thulium-doped fiber amplifier (TDFA), we obtained a high-power pump source with a spectral coverage of 1.9~2.2 μm. We only use 12 cm long 94 mol. % GCF for spectral broadening pumped by TDFA. In addition, we measured the spectral broadening after 12 cm GCF in different length of dispersion compensation fibers (DCF) corresponding to different pulse width and peak power. As a result, we obtained a broadband SC source based on 12 cm 94 mol. % GCF extending from 1630 to 3205 nm and a maximum output average power of 15.07 W with a slope efficiency of 34.2%. The 20 dB spectral bandwidth was over 1000 nm spanning from 1.89 to 2.92 μm. To the best of our knowledge, this is the first demonstration of 15-W level SC laser based on germania-core fiber with long wavelength edge extending beyond 3.2μm. Further broadening of spectrum is limited to pump power.
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