Crack-Free Silicon-Nitride-on-Insulator Nonlinear Circuits for Continuum Generation in the C-Band

We report on the fabrication and testing of silicon-nitride-on-insulator nonlinear photonic circuits for complementary metal-oxide-semiconductor (CMOS) compatible monolithic co-integration with silicon-based optoelectronics. In particular, a process has been developed to fabricate low-loss crack-free Si3N4 730-nm-thick films for Kerr-based nonlinear functions featuring full process compatibility with existing silicon photonics and front-end Si optoelectronics. Experimental evidence shows that 2.1-cm-long nanowires based on such crack-free silicon nitride films are capable of generating a frequency continuum spanning 1515-1575 nm via self-phase modulation. This work paves the way to time-stable power-efficient Kerr-based broadband sources featuring full process compatibility with Si photonic integrated circuits on CMOS lines.