Influence of pulse-width on flat supercontinuum in XPM-assisted dual-wavelength pumping

Dual-wavelength pumping based on cross-phase modulation (XPM) has been experimentally demonstrated to generate broadband, flat supercontinuum (SC) in fiber, but the role of pump pulse width remains unclear. Here, we experimentally and numerically study the propagation dynamics in XPM-assisted dual-wavelength pumping to clarify both the spectral-flattening mechanism and the influence of pulse width. The results show that XPM lowers the modulation-instability (MI) threshold of the 1550 nm pulse, while the resulting MI sidebands are transferred to the 1030 nm pulse through XPM coupling, promoting pulse break-up and subsequent intrapulse Raman scattering at 1030 nm. This process mitigates pronounced cascaded Raman peaks and favors smooth broadband spectrum generation. The pulse width of dual-wavelength pumping determines the effective XPM interaction window and thus the fraction of 1030 nm pulse energy involved in XPM-induced modulation. Consequently, spectral flatness is governed by a trade-off between increasing temporal overlap and maintaining sufficient pulse energy for efficient spectral broadening, leading to an optimal pulse-width pairing. These results provide practical guidance for optimizing flat SC generation in dual-wavelength fiber pumping and offer further insight into the coupled nonlinear dynamics in optical fibers.