Flat supercontinuum spanning 738-2200 nm generation in standard telecom fibers based on dual-wavelength pumping scheme

The high-intensity cascaded Raman peaks and low-intensity short wavelength components are two bottle-neck factors that limit the further spectrum flatness improvement of supercontinuum (SC) in the broadband range. In this paper, we address these challenges by introducing a dual-wavelength pumping scheme based on enhanced cross-phase modulation (XPM). The pump source consists of an ytterbium-doped fiber laser and an erbium-ytterbium co-doped fiber laser. By controlling the output power, the initial pulse synchronized state, and group velocity matching degree of two fiber lasers, we obtain a flat SC spanning the entire wavelength range of 738-2200 nm in a piece of standard telecom fiber. Within the entire wavelength range, the spectrum flatness has been improved to 6.5 dB without the residual pump peak and 10.2 dB with the residual pump peak, respectively. To the best of our knowledge, the dual-wavelength pumping scheme based on XPM is first introduced to SMF28e and the flatness is improved from 20 dB to 10.2 dB in similar spectrum range compared to reported SMF28e-based SC. This work provides a cost-effective method to realize a flat and broadband SC independent of fiber design, and it also establishes a research foundation for obtaining the high-performance SC at higher power levels.