High-efficiency photon-pair production is a long-sought-after goal for many optical quantum technologies, and coherent photon conversion (CPC) processes are promising candidates for achieving this.We show theoretically how to control coherent conversion between a narrow-band pump Seat Pad photon and broadband photon pairs in nonlinear optical waveguides by tailoring frequency dispersion for broadband quantum frequency mixing.We reveal that complete deterministic conversion as well as pump-photon revival can be achieved at a Accessories finite propagation distance.We also find that high conversion efficiencies can be realised robustly over long propagation distances.These results demonstrate that dispersion engineering is a promising way to tune and optimise the CPC process.