Comparison between theory and experiment of nonlinear propagation for a-few-cycle and ultrabroadband optical pulses in a fused-silica fiber

Wave-propagation equations, including effectively the second derivative in time under the condition of a small difference between the group and phase velocities and the first derivative in position /spl xi/ in the group velocity coordinate, are derived based on the slowly evolving wave approximation. These can describe ultrabroadband optical pulse propagation with not only self-phase modulation (SPM), but also induced-phase modulation (IPM) in the monocycle regime in a fiber. It is shown that linear dispersion effects can be rigorously included in the numerical calculations. Calculations including SPM in a single-mode fused-silica fiber with the Raman effect are performed and compared with experimental results. Also, calculations including IPM in the fused-silica fiber are compared with experimental results. The effects of each term in the calculations on spectra are analyzed and it is shown that inclusion of the Raman effect and the dispersion of the effective core area is important for obtaining better agreement with experiments. It is shown that inclusion of more than third-order dispersion terms is necessary for calculations of monocycle pulse propagation.