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

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