Far-detuned mid-infrared frequency conversion via normal dispersion modulation instability in chalcogenide microwires.

We report the observation of modulation instability (MI) in the mid-infrared (mid-IR) spectral region by pumping a hybrid polymer-chalcogenide optical microwire with a femtosecond optical parametric oscillator operating at 2.6 μm. It is further shown that this MI occurs in the normal dispersion regime through negative fourth-order dispersion and leads to far-detuned parametric frequency conversion at 2 and 3.5 μm, despite the presence of a strong absorption band around 2.8 μm. Stochastic nonlinear Schrödinger equation simulations of mid-IR MI are in excellent agreement with experiments.