Experimental and numerical analysis of widely broadened supercontinuum generation in highly nonlinear dispersion-shifted fiber with a femtosecond pulse

Abstract

We report the analysis of ultrawideband supercontinuum generation in a highly nonlinear dispersion-shifted fiber. A >1000-nm-spanning white-light continuum is generated by pumping the femtosecond fiber laser pulse at λ=1.56 μm into the extreme vicinity of the zero-dispersion wavelength of the fiber. The supercontinuum pulses are characterized with the experimentally observed sonogram traces. The numerical calculation based on the nonlinear Schrödinger equation is used to investigate the mechanism of the supercontinuum generation, and these results are in good agreement with experiment. We show that there are two stages with different spectral-broadening processes in the propagation evolution. Self-phase modulation and group-velocity dispersion play an important role in the first spectral broadening. Through an increase the propagation distance, further spectral broadening occurs due to the soliton self-frequency shift and the trapping effect by the redshifted soliton pulse through cross-phase modulation. Additionally, we show that the temporal and spectral interferences between the generated supercontinuum components cause the oscillating fine structure on the temporal waveform and the spectrum.