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 Schrbdinger 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.