A relatively simple master oscillator power fiber amplifier experimental configuration is deployed through seeding of a 2 mW average power single pass optical parametric generator signal at 2.75 μm, driven by a microchip laser, with 400 ps pulses at 2 kHz repetition rate which were amplified in a collinearly pumped Er:ZrF4 double-clad fiber. In a simplification of the system and to make the overall source more robust, the MOPFA output was directly fusion spliced to a slightly multi-moded fluoroindate fiber with approximately 13.5 μm diameter core, in which the supercontinuum was generated. This did incur a splice loss of 20% which was also to limit power scaling of the amplified signal through parasitic oscillation of the amplifier. With the zero-dispersion of the fluoroindate fiber lying around 1.7 μm and the pump at 2.75 μm, modulational instability, soliton formation, Raman gain and soliton self-frequency shifting leading primarily to a long-wavelength extension of the spectrum were the principal mechanisms contributing to the spectrally broadened output. Optimization of the length of the non-linear fiber was undertaken, but the rapidly increasing attenuation beyond 5 μm effectively limited lengths to about 1 meter. The observed spectra also suggested that a second dispersion zero also existed in the fiber around 4 μm or possibly higher-order modes could have contributed to the spectral shaping of the long-wavelength extension of the continuum. With the potential for power scaling, however, such a compact and relatively simple source with 80% of the power lying beyond 3 μm could find wide application.
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