Measurement of the Kerr Nonlinear Refractive Index and its Variation Among <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mn>4</mml:mn><mml:mi>H</mml:mi></mml:math>-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mi>Si</mml:mi><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:math> Wafers
Jingwei Li, Ruixuan Wang, Lutong Cai, Qing Li
Abstract
The unique material property of silicon carbide ($\mathrm{Si}\mathrm{C}$) and the recent demonstration of low-loss $\mathrm{Si}\mathrm{C}$-on-insulator integrated photonics platform have attracted considerable research interests for chip-scale photonic and quantum applications. Despite the impressive progresses made in $\mathrm{Si}\mathrm{C}$ photonics, some of its beneficial photonic properties are yet to be fully explored. Here, we carry out a thorough investigation of the Kerr nonlinearity among $4H$-$\mathrm{Si}\mathrm{C}$ wafers from several major wafer manufacturers, and reveal that their Kerr nonlinear refractive index can be significantly different. By eliminating various measurement uncertainties in the four-wave mixing experiment, the best Kerr nonlinear refractive index of $4H$-$\mathrm{Si}\mathrm{C}$ wafers is estimated to be approximately 4 times, instead of the prior estimate of 2 to 3 times, of that of stoichiometric silicon nitride in the telecommunication band. In addition, experimental evidence is developed that the Kerr nonlinearity in $4H$-$\mathrm{Si}\mathrm{C}$ wafers can be stronger along the $c$ axis than that in the orthogonal direction. Our examination of the Kerr nonlinear refractive index also compels a useful correction to the existing model in high-index-contrast waveguides; otherwise, considerable errors can be introduced.