Strong third-order nonlinearity in amorphous silicon carbide waveguides.

Silicon carbide (SiC) photonic integrated platform has attracted significant research interest for on-chip optical applications, owing to its exceptional optical properties such as a broad transparency window, high refractive index, and strong nonlinearity. Among the various types of SiC, amorphous SiC (a-SiC) has particularly emerged as an accessible choice for forming thin-film SiC-on-insulator (SiCOI) stacks, demonstrating promising capabilities for wafer-scale photonic applications. In this work, we prepare three a-SiCOI samples using the plasma-enhanced chemical vapor deposition, with different refractive indices. We fabricate optical waveguides, conduct four-wave mixing measurements, and characterize the nonlinear refractive index in these samples. Our findings reveal that an increase in the refractive index of a-SiC leads to a corresponding increase in the nonlinear refractive index, which is comparable to that of silicon. Hence, a-SiC offers an approach to develop a SiC platform with a wider bandgap than that of silicon, minimizing two-photon absorption while also providing a higher refractive index and stronger nonlinearity compared to crystalline SiC.