Investigation of Kerr nonlinearity in multi-layered silicon nitride waveguides

Silicon nitride is a promising waveguide platform for harnessing Kerr nonlinearity due to the low propagation loss, wide transparency range, and negligible two-photon absorption effect in the telecom wavelength range. However, the values of Kerr nonlinear coefficient of various low loss silicon nitride waveguide structures are not well defined. In this work, we perform numerical and experimental investigations of Kerr nonlinearity coefficients of multi-layered silicon nitride (Si3N4) waveguides. Three distinct geometries were considered, namely asymmetric double stripe (ADS), symmetric double stripe (SDS), and thick Si3N4 waveguides. The numerical investigation was done using three different models: scalar, vectorial, and perturbative models. The Experimental investigations were carried out using four-wave mixing experiments. We found good agreement between the theoretical and experimental results, leading to silicon nitride Kerr index of 1.644 × 10−19 W−1m2.