Numerical Investigation of Idler Pulse Generation by Four-Wave Mixing in Nonlinear Optical Ring Resonator

Generation of idler pulses via the four-wave mixing (FWM) effect in a nonlinear optical ring resonator (NORR) was investigated numerically. It was found that the relative delay τ between input pump pulses significantly affects both the energy and temporal–spectral characteristics of generated idler pulses. Specifically, idler pulse energy decreases with increasing τ due to phase-matching conditions in FWM. Maximum energy transfer occurs for τ = 0, where optimal phase alignment among pump, signal, and idler waves is achieved. Temporal and spectral analysis at different relative delays reveals a change from a symmetric, multi-subpulse structure with a comb-like spectrum (for τ = 0) to a near-single-pulse form with a single-comb-line spectrum (for τ = 9 ps). These findings demonstrate the critical dependence of FWM efficiency on pump pulse synchronization. Therefore, precise control of the relative delay is essential for optimizing idler pulse generation in NORRs.