放电引发非链式DF激光器关键技术研究

	放电引发非链式DF激光器关键技术研究
	潘其坤
学位类型	博士
导师	谢京江,谢冀江
	2014-07
学位授予单位	中国科学院大学
学位专业	光学工程
摘要	氟化氘（DF）激光器输出波长（3.5～4.1μm）处于大气透射窗口，它是激光雷达、激光光谱学、激光与物质相互作用等领域急需的中波红外激光光源。本文围绕重复频率非链式DF激光器，重点研究了大体积均匀辉光放电，光学谐振腔，重复频率运转及尾气处理等关键技术。在此基础上，进行了DF激光器增益系数测量、光谱特性分析及激光器输出性能优化实验研究，为研制具有实用价值的非链式DF激光器奠定了基础。为了实现大体积均匀辉光放电，研究了火花针紫外预电离放电引发非链式DF激光器（采用LC反转电路）的放电特性。采用电子连续性方程与基尔霍夫回路方程建立了描述DF激光器放电特性的数学模型，并对理论模型进行了实验验证，发现理论与实验结果相符。进而运用该模型仿真获得了有利于提升注入能量的电路参数。为了获得更大间隙的辉光放电，引进了“自引发”放电方式，它采用一种倍压式反转电路和粗糙阴极结构，无需预电离装置即可实现大体积均匀放电。建立了能够描述倍压式反转电路放电特性的数学模型，实验与模拟结果均显示，“自引发”放电引发方式具有实现更大间隙辉光放电的潜力。谐振腔参数对激光器输出性能和抗失调特性影响显著，理论分析了平凹腔光束宽度、远场发散角、失调灵敏度及有效模体积随后反射镜曲率半径的变化关系，获得了最佳的后反射镜曲率半径参数。同时设计了三组正分支非稳定共焦腔参数，并分析了其失调特性。运用烧蚀法获得了平凹腔与非稳腔的近、远场光斑，实验测量的远场发散角分别为6mrad、1.2mrad。 DF激光器在封闭循环运转时，单次充气寿命较短，工作物质的消耗和放电产物的消激发作用是导致激光输出性能下降的主要因素。提出了一种可实时梯次更新工作气体的技术方案，并分析了化学吸附剂消除放电产物中消激发作用最显著的DF分子的可行性方案。采用分子筛吸附剂和工作气体实时更新系统，可有效提升激光器输出稳定性。通过分析DF激光器放电过程中发生的化学反应，发现其工作尾气中的有害成分主要为DF及SF4。进而分析了碱性溶液洗消DF及SF4的原理，并设计了一种小型化尾气洗消装置，处理后的工作尾气可达到国家安全排放标准。考虑了谱线加宽对增益系数的影响，推导了运用变耦合率法计算DF激光器增益系数的算法，并运用该算法实验研究了DF激光器横截面上的二维增益分布。运用DF激光谱线分析仪测量了DF激光器的输出光谱，在3.5～4.1μm范围内测得了22条谱线。对自引发放电非链式DF激光器工作气体参数进行了优化实验，在工作气体配比SF6:D2=8:1，充气总气压为8.1kPa时：获得的最大单脉冲能量为3.6J，脉冲宽度为135ns，峰值功率为26.67MW，电光转换效率为3.1%；50Hz重频运转时获得的最大输出功率为150W，电光转换效率为2.58%，激光脉冲幅值差小于±8%。
其他摘要	The DF laser radiation is concentrated in the spectral range 3.5～4.1μm (“transparency window” of atmosphere), which is a useful medium waves infrared laser badly needed in laser radar, laser spectroscopy, laser interaction with matter, etc. Arounding repetitive frequency DF laser, the study was focused on key technologies of massive uniform discharge, optical resonator, repetition rates operation, tail gas treatment, etc. On this basises, the measurement of gain coefficient, analysis of spectral character and optimizing experiment of output performance had been done, which could lay a foundation for practical design of non-chain DF laser. The circuit parameters of spark pin UV pre-ionization discharge non-chain pulsed DF laser (LC reverse circuit) were researched to realize the massive uniform glow discharge. Mathematical model had been established to describe its discharge parameters using continuity-equations of electrons and Kirchhoff equations. Then the corresponding experiments were carried out to verify the results of this model and the optimal circuit parameters of DF laser were obtained on theory. To obtain a bigger gap glow discharge, the self- -initiated volume discharge (SIVD) was imported, which realized the massive uniform glow discharge without preionization by using a voltage-doubling circuit and roughened cathode. A mathematical model was established to describe the discharge parameters of this circuit. Both the experiment and calculation showed that it was easy to realize massive uniform glow discharge with SIVD. The parameters of resonator have marked influences on output performances and anti-misalignment of mirrors.The dependence of some parameters on curvature radius of rear mirror had been analyzed, such as beam width, beam divergence angle, misalignment sensitivity, effective mode volume, and then the optimum curvature radius of rear mirror was obtained. Three groups of unstable confocal cavity parameters had been designed and their characteristics of misalignment were analyzed. The laser spots of stable and unstable cavities had been measured using the method of laser ablation, the beam divergence angle of which were 6mrad and 1.2mrad individually. When DF laser works at closed cycle, its working life of single gas-filled was very short. Consumptions of working gas and deexcite collisions of discharging products were major factors for output energy lowers of DF laser. A technical scheme which would realize real-time refresh of working gas had been introduced and feasibility study for chemical scrubber adsorbing DF molecular, which deexcite effect was the most significant in the discharging products, had been done. Using the refresh equipment of working gas and chemical scrubber could increase working stabilization of DF laser. Through analyzing the chemical process which was occured in discharge area of DF laser, we found that the harmful ingredient in tail gas were DF and SF4. The principle of alkaline solution removing DF and SF4 was analyzed, and miniaturized tail gas processing equipment was designed. The tail gas could meet national safety effluent standard after treating. Based on the influence of spectral lines broadening on gain coefficient, the algorithm which was used to calculate gain coefficient of DF laser had been deduced using the variable output coupling method. Gain distribution on the cross-section of gain medium was researched on experimentally using this algorithm. The DF laser spectrum analyzer was used to measure the output spectrum of DF laser, and 22 lines were obtained in the spectial range: 3.5～4.1μm. Working gas parameters were optimized for non-chain DF laser. The total pressure and optimum ratio of the mixture gas (SF6-D2)，are 8.1kPa and 8:1，respectively. The maximum single pulse energy of 3.6J, pulse width of 135ns, peak power of 26.67MW and electro-optical conversion efficiency of 3.1% are achieved. The maximum average power of 150W and electro-optical conversion efficiency of 2.58% are achieved at 50 Hz, whose amplitude difference of laser pulses is better than 8%.
语种	中文
文献类型	学位论文
条目标识符	http://ir.ciomp.ac.cn/handle/181722/41454
专题	中科院长春光机所知识产出
推荐引用方式 GB/T 7714	潘其坤. 放电引发非链式DF激光器关键技术研究[D]. 中国科学院大学,2014.

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