【作者】 朱国利；

【导师】 王月珠；

【作者基本信息】 哈尔滨工业大学 ， 物理电子学， 2012， 博士

【摘要】 自从20世纪60年代少数研究者对掺Ho激光器进行介绍之后，Ho³⁺离子因其特殊的光谱特性，如长的激光上能级寿命、可以获得人眼安全和大气高透过率的2.1μm激光等，使它成为产生激光的重要离子。2.1μm激光在医学、军事、机械加工和遥感等方面均有重要的应用，特别地，2.1μm激光可通过泵浦非线性晶体有效获得光电对抗源中红外3⁵μm激光和远红外8¹2激光。为获得高功率高重频中红外3⁵μm激光，本文对2.1μm Ho:YAG激光器及其泵浦源Tm:YLF激光器进行了理论分析和实验研究。理论方面，分析了单掺Tm³⁺激光和单掺Ho³⁺激光的能级跃迁机制和发光机理，建立了单掺Tm³⁺激光和单掺Ho³⁺激光速率方程理论模型，并依据速率方程模型分析了各种参数对Tm:YLF激光器和Ho:YAG激光器输出特性的影响。分析了影响固体激光器弛豫振荡频率和弛豫振荡幅度的各种理论因素，为有效解决Tm:YLF激光器的弛豫振荡问题奠定了理论基础，为Tm:YLF激光器弛豫振荡问题的实验研究提供了重要的理论指导。分析了Tm:YLF晶体和Ho:YAG晶体的温度场和理论热焦距长度，为实现Tm:YLF激光器和Ho:YAG激光器的谐振腔优化设计提供了必要的参数。分析了Tm:YLF晶体的热致损伤阈值问题，为获得Tm:YLF激光器可承受的最大泵浦功率值提供了理论参考。实验方面，对Tm:YLF和Ho:YAG晶体的热透镜焦距以及Tm:YLF晶体的热致损伤阈值进行了测量，为Tm:YLF和Ho:YAG激光器谐振腔的设计以及Tm:YLF晶体最大可承受泵浦功率提供了参考数据。测试了输出镜透过率、泵浦-激光模式比率对Tm:YLF激光器功率特性的影响，并依据对测试结果的分析进行了高效率腔内双晶体和高功率、高光束质量腔内三晶体Tm:YLF激光实验，腔内双晶体Tm:YLF激光器的斜率效率达到49.4%。在Tm:YLF弛豫振荡实验中，测试了泵浦功率、腔长和输出镜反射率对弛豫振荡频率的影响，测试了泵浦功率和泵浦-激光模式比对弛豫振荡幅度的影响，通过对Tm:YLF弛豫振荡问题的实验研究，实现了高效率高功率Tm:YLF激光器功率信号的平滑无尖峰输出，排除了Ho:YAG激光器高重频几十千赫兹工作时的障碍。根据对腔内单晶体和腔内双晶体Ho:YAG激光器谐振腔参数的理论分析进行了高功率Ho:YAG激光器实验研究工作，利用两种结构的激光谐振腔均获得了平均功率大于40W的2.1μm激光，转换效率均约为50%，证明了百瓦级腔内双晶体Ho:YAG激光器的可行性。通过对键合和非键合Ho:YAG晶体的实验对比，发现键合Ho:YAG晶体的转换效率略高于非键合晶体，实验上证明了键合Ho:YAG晶体在高功率泵浦时的优势。最后，利用腔内单晶体Ho:YAG激光器进行了ZGP OPO的泵浦实验，OPO的斜率效率达到51.6%，光-光转换效率达到42.1%，利用刀口法测得3⁵μm激光10W时的光束质量因子M²为4.2，利用HgCdTe探测器测得16.0W时3⁵μm激光脉冲宽度为18.5ns，考虑到实验结果与国际先进水平的差距，提出了改善中红外ZGP OPO效率和光束质量的方法。更多还原

【Abstract】 After a few researchers have introduced Ho-doped lasers, Ho³⁺ions have becomethe important ions which can be used of lasers because of their special spectralcharacteristics, such long lasers’ upper level lifetime, getting eye-safe and atmospherehigh transmittance2.1μm laser etc. since the1960s. In medicine, military, mechanicalprocessing and remote sensing fields,2.1μm lasers have important applications. Inparticular,2.1μm lasers can effectively get optoelectronic countermeasure sourcemiddle infrared3⁵μm lasers and far infrared8¹2μm lasers by pumping nonlinearcrystal. In order to obtain high power&high repetitive frequency middle infrared3⁵μm lasers, this article analyses and researches2.1μm Ho:YAG laser and it’s pumpsource Tm:YLF laser in theory and experiment.In the aspect of theory, the energy level transition mechanism and laser emittingmechanism of single-doped Tm³⁺laser&single-doped Ho³⁺laser are analysed, the rateequation theoretical model of single-doped Tm³⁺laser&single-doped Ho³⁺laser areestablished, and all kinds of parameters’ effect on Tm:YLF laser&Ho:YAG laser’soutput characteristics according to rate equation model are analysed. All kinds oftheoretical factors that effect on solid-sate laser relaxation oscillation frequency andrelaxation oscillation range are analysed, establishing the theory basis for solvingTm:YLF lasers’ relaxation oscillation issue effectively, providing the significanttheoretical guidance for Tm:YLF laser relaxation oscillation issue’s experimentalresearch. The temperature field and the theoretical thermal focal length of Tm:YLFcrystal&Ho:YAG crystal are analysed, providing the necessary parameters for realizingthe resonant cavities’ optimization design of Tm:YLF laser&Ho:YAG laser. thethermal damage threshold issue of Tm:YLF crystal is analysed and providing thetheoretical reference for obtaining Tm:YLF laser’s maximum pump power value.In the aspect of experiment, the thermal lens focal lengths of Tm:YLF&Ho:YAGcrystal and thermal damage threshold of Tm:YLF crystal are measured and providingthe reference data for Tm:YLF&Ho:YAG laser resonant cavities’ design and Tm:YLFcrystal’s maximum pump power value. The output-mirroro transmission&pump-lasermodel ratio’s effect on Tm:YLF power characteristics are tested, an effective cavitybicrystal and high power&high beam quality cavity tricrystal laser are conductedaccording to the analysis of test result, and the slope efficiency of49.4%is obtained inthe Tm:YLF laser with bicrystal cavity. During the Tm:YLF relaxation oscillationexperiment, the pump power and cavity length&output-mirroro transmission’s effecton relaxation oscillation frequency are tested, pump power and pump-laser model ratio’seffect on relaxation oscillation range are tested. By the experiment research for Tm:YLF relaxation oscillation issue, realising the high efficiency&high power Tm:YLF laserpower signal’s smooth output without peak and remove the working obstacles whenHo:YAG laser works at high repetitive frequency of some dozen kilohertz. According tothe single-crystal and bicrystal Ho:YAG laser resonant cavity parameter’s theoreticalanalysis, high power Ho:YAG laser experimental research work is conducted. Averagepower of more than40W and conversion efficiency of⁵0%are realized in both ofsingle-crystal and bicrystal Ho:YAG laser resonant cavity. One hundred watt bicrystalHo:YAG resonant cavity is proved feasible. By bonding and nonbonding Ho:YAGcrystal’s experiment comparision, finding bonding Ho:YAG crystal’s conversionefficiency is a little bit higher than that of nonbonding crystal. That proves bondingHo:YAG crystal’s advantage with high power pump. At last, by single-crystal Ho:YAGlaser resonant cavity, the ZGP OPO is experimented, and then OPO slope efficiencyreaches51.6%&optical-optical conversion efficiency reaches42.1%. By knife-edgemethod, the3⁵μm laser’s beam quality factor （M²） of4.2with10W is measured. ByHgCdTe detector, the3⁵μm laser’s pulse width of18.5ns with16.0W is measured.Finally, considering the lower level of experimental result compared with internationaladvanced level, putting forward the methods of improving middle infrared ZGP OPOefficiency and beam quality.更多还原