Four-wave mixing in silicon-nanocrystal embedded high-index doped silica micro-ring resonator

A nonlinear integrated optical platform that allows the fabrication of waveguide circuits with different material composition, and at small dimensions, offers advantages in terms of field enhancement and increased interaction length, thereby facilitating the observation of nonlinear optics effects at a much lower power level. To enhance the nonlinearity of the conventional waveguide structure, in this work, we propose and demonstrate a microstructured waveguide where silicon rich layer is embedded in the core of the conventional waveguide in order to increase its nonlinearity. By embedding a 20 nm thin film of silicon nanocrystal (Si-nc), we achieve a twofold increase of the nonlinear parameter, γ. The linear relationship between the four-wave mixing conversion efficiency and pump power reveals the negligible nonlinear absorption and small dispersion in the micro-ring resonators. This simple approach of embedding an ultra-thin Si-nc layer into conventional high-index doped silica dramatically increases its nonlinear performance, and could potentially find applications in all-optical processing functions.