The Establishment and Evolution of Four-Wave Mixing Process in Time Lens

This study elucidates the dynamic evolution of degenerated four-wave mixing (FWM). The direct observation of the FWM establishment process reveals a dual-stage cascade mechanism with distinct thresholds in high nonlinear fiber (HNLF): idler generation can be observed after 3000 round trips (RTs&171μs) when pump/signal powers exceed threshold, triggering a secondary stage after another observable∼1000 RTs&56.2μs forming a multi-peak spectrum. While self-phase modulation (SPM) broadens the pump spectrum (3 nm to 6 nm), its phase-only nature minimally impacts time lens (TL) imaging. This research focuses on addressing a specific physical problem: how the nonlinear dynamics (including thresholds, cascade establishment, etc.) in a standard four-wave mixing system composed of highly nonlinear optical fibers can be observed and understood in real time within the “TLD-DFT” framework, which offers high temporal resolution for measurements.