High-power mid-infrared supercontinuum generation using germania-core fiber

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.