超短脉冲光束的传输特性研究

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1、西南交通大学硕士学位论文超短脉冲光束的传输特性研究姓名：柳红英申请学位级别：硕士专业：通信与信息系统指导教师：罗斌20070501西南交通大学硕士研究生学位论文第1I页冲光束自聚焦特性的影响．由于时空耦合与介质色散有关，使得群速度色散GVD和三阶色散TOD都会引起时间脉冲的另一延迟。轴上时间波形向轴外偏移，成为旁轴脉冲，其偏移量缸与传播距离、色散成正比，随着传播距离的增大，脉冲的傍轴延迟相应增大，色散越大，傍轴延迟越大．TOD和GVD也都引起脉冲展宽，光强下降，TOD同,GVD的影响相比，脉冲展宽更快，强度下降也更多，且TOD

2、使脉冲产生不对称，后沿有一个长的拖尾。而这时空间光强分布由于受到脉冲延迟的影响，中心轴上的光强极小，近场空间分布几乎没有发生变化，可见色散较好地抑制了自聚焦效应。关键词：超短超强脉冲光束；菲涅耳衍射；时空聚焦；自陡峭效应；自聚焦西南交通大学硕士研究生学位论文第1

3、I页AbstractWiththerapiddevelopmentoflaserdrivertechnologyininertialconfinementfusionOc职ultrashortpulsedbeamswemappHedinhighpowerlasersy

4、stemgradually．Inultrashortpulsedbeamspropagation,generallyspeaking,small-scaleself-focusingwasrestrainedpreferably．Andthebandwidthofultrashortpulsedbeamsleadstomanynewquestions．Thereforethestudyofultrashortpulsedbeamshasbeenafocusofthescientificresearch．Onthebasisof

5、themodified(3+1)-dimensionalnonlinearSchrodingerequation，symmetryspmFouriertransformmethodasthemethodofnumedcalsimulation,weinvestigatethepropagationoffemtosecondpulsedbeamsinfreespaceandnonlineardispersivemedia．Themainresultsachievedinthistheslscanbe辄玎nnlaIizedasfo

6、llows：1．TheNear-fieldFresneldiffractionmodulationofultrashortpulsedbeamsinfreespaceisstudiedintheorybyuseofthesimulation．TheFresneldiffractionpattemofregularshapesScreensuchasrectangularaperture，serratedcircleapertureandSuper-Gaussianbeam．Thediffractionmodulationofu

7、ltrashortpulsed-laserislessthanCWlaser：Andthetransmissionfeaturesoftheultra-shortpulsed-laserpassingthroughtheserratedapertureandspatialfilterisstudiedinallusiontocleanandllnifb眦intensitydistributioninthehigh-energyultrashortpulse-lasersystem．especialdiffractionofSu

8、per-Ganssianbeam．Theresultshow：Theaxialpulseenvelopepropagatesundistortedwhenpropagatinginfreespace．butthespatiotemperalcouplingcanaffectitsintensity．2．Theself-focnsingpropertiesoffemtosecondpulsesinanonlineardispersivemediumisinvestigatednumericallyintheregimewhere

9、thecombinedeffectsofdiffraction,Space-timecoupling,normaldispersion,andcubicnoulmearityleadtopulsesplitting．Themainworkandachievementsasfo