脉宽对不同密度介质中传播的超短脉冲特性的影响

Effect of pulse width on ultrashort pulse propagation characteristics in the media with different densities

利用使用预估校正(PC)-时域有限差分(FDTD)法求得的全波Maxwell-Bloch方程组的数值解,研究脉宽对在不同密度的V型三能级介质中传播的飞秒超短激光脉冲特性的影响。结果表明,不同原子密度情况下,脉宽改变对脉冲传播特性的影响是不同的。当超短脉冲在原子密度较小的稀疏介质中传播时,脉冲不易发生分裂;当脉冲未分裂时,随着脉宽的增大,脉冲振幅明显减小。当超短脉冲在原子密度很大的稠密介质中传播时,脉冲较易发生分裂;随着脉宽的增大,脉冲分裂的子脉冲个数增多,脉宽的增大也加速了脉冲的分裂。

The effect of pulse width on propagation characteristics of the femtosecond ultrashort laser pulse in V-type three-level atomic media with different densities is investigated by using the numerical solution,which is obtained by PC-FDTD method for the full Maxwell-Bloch equation. It is shown that the effect of the pulse width on propagation characteristics of the pulse is different for different atomic density cases. When the ultrashort pulse propagates in the dilute medium with smaller atomic density, the pulse is not easy to split. When the pulse doesn＇t split, the pulse amplitude will decrease obviously with the pulse width increasing. When the ultrashort pulse propagates in the medium with very large atomic density,the pulse is easy to split,and the number of sub-pulses increases with the pulse width in- creasing Moreover the increase of the pulse width accelerates the pulse splitting.