Wavelength tunable ultra-short pulses based on a flat broadband spectrum generated in a nonlinear ytterbium-doped fiber amplifier
Xu Run-Qin, Dong Zi-Kai, Tian Jin-Rong, Li Ke-Xuan, Song Yan-Rong
       

(color online) Output spectra corresponding to different pump powers. The inset is the same spectrum in linear scale.