Silicon nitride has recently attracted significant interest for nonlinear integrated optics. In addition to its excellent linear properties, silicon nitride offers a bandgap larger than silicon, and a wide transparency window spanning from the visible all the way to the middle infrared (mid-IR). As such, research efforts have been focused on leveraging these properties in order to achieve efficient nonlinear wave-mixing of the third and second order. In this paper we will show how mid-IR light can be efficiently generated in large cross section silicon nitride waveguides through careful dispersion engineering and how second order nonlinearities can be significantly enhanced through an all-optical poling process.