Multimode Phase Matching and Overlap Engineering in Gallium Selenide on Silicon Nitride Hybrid Waveguides for Spontaneous Parametric Down Conversion

We present the design and performance analysis of hybrid waveguides comprising of multilayer Gallium Selenide on silicon nitride waveguides for spontaneous parametric down-conversion (SPDC)-based photon pair generation. By choosing appropriate waveguide dimensions, we achieve multimode phase matching and optimize the modal overlap for achieving increased photon pair generation rates. Our SPDC model includes the effects of waveguide propagation losses and phase mismatch on the photon pair generation rate. The model predicts photon generation rates as high as 13 KHz from just 50 µm section of the hybrid waveguide under multimode phase matching of TE01 and TE00 modes for the pump and signal-idler respectively.