大模场光纤波导特性的理论研究

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1、天津大学博士学位论文大模场光纤波导特性的理论研究姓名：谭晓玲申请学位级别：博士专业：光电子技术指导教师：姚建铨20090501特性，并与相同结构参数时圆空气孔光子带隙光纤耦合长度、无耦合情况进行了比较。对双芯环状结构全固态光子带隙的耦合特性进行了理论分析。分析了不同入射情况下三芯光子晶体光纤的耦合特性，以及耦合长度对光纤结构参数的敏感性，为光子晶体光纤激光器的相干合成技术提供了理论依据。关键词：高功率光纤激光器大模场光纤增益导引光纤光子晶体光纤光子带隙光纤模式截止弯曲损耗ⅡABSTRACTHighpow

2、erfiberlasershaveincitedparticularinterestasefficient,compactlaserswithgoodbeamqualityforavarietyofapplicationsinindustryprocessing，medicalinstrumentsandnationaldefense．However,afurtherpowerscalingoffiberlasersismainlylimitedbyvariousnonlineareffectsinfi

3、bers，andtheobviouswaytoreducethenonlinearityandincreasethepoweristouselargemodearea(LMA)fibers．WiththeCOresizeincreasing，theobstaclesforhi}ghpowerfiberlasersaremulti-modeoperationandbend-inducedmodedistortion．Soitisverysignificanttoinvestigateanddesignbe

4、nd-resistant，single—modelargemodeareafiberstofurtherenhancethepoweroffiberlasers．Themaincontentsandkeycreationpointsofthisdissertationareasfollows：1．Byinvestigatingthewaveguidingcharacteristicsofgain—guidedfibers，thecutoffconditionsofdifferentmodesasfunc

5、tionofgain—coefficientandindexstepareobtained．Theeffectoftheresonatormirrorreflectivityongain-guidedandindex—antiguidedfiberlasershasbeendiscussed．Themodefielddistributionsvaryingwithgaincoefficientandnegativeindexstep，andthemodeconfinementcapabilityinga

6、ill—guidedfibershavealsobeeninvestigated，whichishighlyinstructivefordesigninglargemodeareafiberwithcoresizeaslargeasseveralhundredmeters．2．Throughanalyzingthecutoffpropertiesoffundamentalmodeandsecondmodebyeffectiveindexmethod，effectiveareamethodandconfi

7、nement’lossmethod，thephasediagramsofcut-offmode，singlemodeandmulti—modeforphotoniccrystalfibersareobtained，andthecomparisonamongthethreemethodsalsohasbeenmade．Anoveloctagonalphotoniccrystalfiberisdesigned，andcomparedwithhexagonalphotoniccrystalfiber，whic

8、hhasmorecircularfelddistribution，widersinglemodeoperationregionandhasadvantageindesigningdispersion-compensatingfiber．3．Inthispaper,thecharacteristicsofbentlargemodeareaphotoniccrystalfibersareinvestigatedcomprehensively．N