Second- and third-order nonlinear wavelength conversion in an all-optically poled SiN waveguide.

Silicon nitride (SiN) is commonly employed to integrate third-order nonlinear optical processes on a chip. Its amorphous state, however, inhibits significant second-order nonlinear response. Recently, second-harmonic generation enhancement has been observed in SiN waveguides after an all-optical poling (AOP) method. Here we demonstrate that, after AOP of a SiN waveguide, for up to 2 W of coupled pump power, the same telecom-band signal undergoes larger interband wavelength conversion efficiency, based on sum-frequency generation (SFG), than intraband wavelength conversion, based on four-wave mixing. We also confirm the appearance of a phase-matching condition after AOP by measuring the conversion bandwidth and efficiency of SFG at different pump wavelengths.