Effect of pulse walk-off on femtosecond pulse compression in photonic crystal fibers

In order to study the influence of pulse walk-off on femtosecond signal pulse compression in photonic crystal fibers, the coupled nonlinear Schrdinger equations were numerically solved by means of standard split-step Fourier method. The nonlinear propagation of two femtosecond optical pulses in a photonic crystal fiber was simulated. The effect of pulse walk-off and asynchronous coupling on signal pulse compression was simulated and analyzed. It is found that the signal pulse can be compressed through the cooperation by group velocity dispersion, third-order dispersion, self-phase modulation and cross-phase modulation, when the pump pulse is input in the anomalous dispersion region while the signal pulse is input in the normal dispersion region. Pulse walk-off not only leads to the degradation of the compression ratio of the signal pulse but also leads to a longer fiber length at which the width of the compressed signal pulse is the minimum, and leads to the non-symmetry of the compressed signal pulse. It is also found that the quality factor of the signal pulse will be improved with the asynchronous coupling method.