Disorder robust, ultra-low power, continuous-wave four-wave mixing in a topological waveguide

Four-wave mixing is a widely used nonlinear process for wavelength conversion, parametric amplification and signal regeneration in various Kerr devices, which enables wavelength-tunability and lower-power operation in compact optical systems. Here, we demonstrate low-power continuous-wave four-wave mixing in an ultra-silicon-rich nitride topological waveguide leveraging the strong confinement of the Su-Schrieffer-Heeger topological structure and ultra-silicon-rich nitride platform's high Kerr nonlinearity and negligible nonlinear loss. We experimentally observe continuous-wave four-wave mixing at an ultra-low pump power of 510 µW, and wavelength tunability of 54 nm with on/off conversion efficiency of -57 dB at a pump power of 3 mW. We further investigate the efficiency of the four-wave mixing process when disorder is introduced into the Su-Schrieffer-Heeger waveguide array resulting in ±80 % randomness in the coupling coefficients. It is experimentally shown that similar conversion efficiencies are achieved in the presence and absence of disorder, indicating robustness against potential fabrication errors. We expect that this work can be applied to develop compact, tunable wavelength conversion systems operating at very low power levels which are robust against certain types of disorder.