Parametrically Tunable Mid-Infrared Resonant Radiation by Four-Wave Mixing in Silicon Nitride Nanophotonic Waveguides

The direct generation of mid-infrared light is of significant interest for various applications including spectroscopy, detection system, optical sensing and biophotonics. Ultrashort-pulse nonlinear interaction can be viewed as four-wave mixing process, which can generate new spectral components under appropriate conditions. Here, we numerically demonstrate a fully, yet effective, spectral conversion scheme where the effective portion and components of femtosecond pulses can access the mid-infrared region directly by four-wave mixing process in silicon nitride integrated photonics waveguide. Wideband conversions occur mainly towards the mid-infrared region around the traditional red-shift phase-matching point without the adjustment of waveguide geometry. The corresponding conversion mechanisms can be attributed to nonlinear interaction of optical waves, resulting in the dispersive wave generation, the soliton-probe collision and the phase-sensitive scattering process. Our results provide an alternative route to realize wideband tunable mid-infrared frequency conversion in silicon nitride system on a chip.