Quasi-phase matching for a nonlinear photonic waveguide enabled by monolayer transition-metal dichalcogenide arrays

Quasi-phase matching (QPM) enables flexible and efficient second-order nonlinearity ranging from bulk nonlinear crystals to integrated nonlinear photonic devices. Here, we propose a QPM nonlinear photonic device constructed using monolayer transition-metal dichalcogenide (TMDC) arrays attached on a silicon nitride waveguide. QPM second harmonic generation comes from a nonlinear interaction between evanescent fields of fundamental-frequency and second-harmonic guided modes with periodical monolayer TMDC arrays. Dispersions of the device can be tuned by changing the geometric parameters of the waveguide while the nonlinear overlap integral and the QPM condition can be controlled through the distribution of TMDC arrays. Our design provides a practical way to efficiently shape second-order nonlinearities in complementary metal–oxide–semiconductor-compatible photonic platforms.