High-power mid-infrared high repetition-rate supercontinuum source based on a chalcogenide step-index fiber

We demonstrate a tunable and robust femtosecond supercontinuum source with a maximum output power of 550 mW and a maximum spectral width of up to 2.0 μm, which can cover the mid-infrared region from 2.3 μm up to 4.9 μm by tuning the pump wavelength. As2S3 chalcogenide step-index fibers with core diameters of 7 and 9 μm are pumped at different wavelengths from 2.5 μm up to 4.1 μm with femtosecond pulses by means of a post-amplified optical parametric oscillator pumped by an Yb:KGW laser. The spectral behavior of the supercontinuum is investigated by changing the pump wavelength, core diameter, fiber length, and pump power. Self-phase modulation is identified as the main broadening mechanism in the normal dispersion regime. This source promises to be an excellent laboratory tool for infrared spectroscopy owing to its high brilliance as demonstrated for the CS2-absorption bands around 3.5 μm.