Supercontinuum generation of femtosecond pulse in high nonlinear fiber

The supercontinuum generation in high nonlinear fiber with the normal dispersion is investigated using the split-step Fourier method.The effect of the peak power of pump pulse,pulse width and the frequency chirp on characteristics of supercontinuum spectrum is analyzed.The results show that the pulse width,peak power and initial chirp of the pump pulse are very important to flat wideband supercontinuum generation.With the increase of the peak power,the spectral width becomes wider(170 nm to more than 400 nm at -20 dB) and the flatness of supercontinuum becomes better.By contrast,the spectral width becomes narrower and the flatness of supercontinuum becomes worser when the pulse width increases gradually.The negative initial chirp is profitable for spectrum broadening,but the positive chirp has certain impact on spectrum broadening.It is further investigated that a broadband and flat supercontinuum without residual pump is generated from such a high nonlinear fiber pumped at the normal dispersion region.