200 nm Supercontinuum Generated by Subpicosecond Optical Pulses and its Evolution Process Observation

nm superconticnumm (SC) with high flatness (<3 dB) is demonstrated with subpicosecond optical pulses generated by a passively mode locked figure eight laser. The evolution process of SC under different optical pumping power is observed experimentally. Three sequential evolution stages are found: (1) SC spectrum is asymmetrically broadened due to self phase modulation (SPM) and group velocity dispersion (GVD). (2) When the broadened spectrum exceeds the zero dispersion point, cross phase modulation (XPM) and four wave mixing (FWM) will cause symmetrical spectrum broadening. (3) stimulated Raman scattering (SRS) causes the spectrum to broaden toward long wavelength quickly when pumping power is intense enough.