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自陡效应对飞秒脉冲光束自聚焦特性的影响
Influence of self-steepening effect on focusing property of femtosecond pulsed beam
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摘要: 为了研究在非线性正常色散介质中,自陡效应对高强度飞秒脉冲光束自聚焦特性的影响,同时考虑色散、时空聚焦和克尔效应。基于(3+1)维的修正非线性薛定谔方程,采用对称分步傅里叶数值计算方法,分不考虑自陡效应即只有色散、时空聚焦及克尔效应和考虑自陡效应两种情况,对90fs超短脉冲光束的自聚焦特性进行了数值仿真。结果表明,色散、时空聚焦和克尔效应的共同作用会使脉冲分裂成丝,能量减少,脉冲展宽,时空聚焦和色散的相关性使脉冲产生了另一延迟,延迟和传输距离及色散成正比;而自陡效应则可以明显降低脉冲峰值强度,减弱非线性的影响,抑制脉冲自聚焦,使时间波形分裂更小,对脉冲延迟量影响较小。Abstract: The influence of nonlinear shock on the focusing property of femtosecond pulsed beams was studied through numerical simulation by using the modified(3+1)-dimensional nonlinear Schrodinger equation,taking into account of diffraction effects,space-time coupling,normal dispersion,and cubic nonlinearity.The self-focusing properties of the 90fs pulsed beam were analyzed and discussed in the absence and in presence of shock effect respectively.The results show:The space-time coupling,dispersion,and Kerr effect together will cause the pulse filament,amplitude descending and its width broadening.As implied by the functional form,space-time coupling relates to the dispersion will produce a time shift.The shift increases with distance and dispersion,and that the self-steepening effect will result in the peak power decreasing greatly,moreover it will weak the pulse self-focusing effect.
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