放电引发非链式脉冲DF激光机理研究

	放电引发非链式脉冲DF激光机理研究
	阮鹏
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	基于化学反应的DF激光器输出波段为3.5~4.2μm，处于大气红外传输窗口，其覆盖了众多原子及分子的吸收峰，因此在光谱学、激光雷达、大气监测及军事等诸多领域都有重要的应用价值和前景。与传统的链式DF激光器相比，非链式脉冲DF激光器具有无腐蚀性、反应可控不易爆炸、结构紧凑、操作简单、光束质量好等优点，并能实现高功率高能量激光输出，因而近年来受到广泛关注。本文采用理论和实验相结合的方法，对放电引发非链式脉冲DF激光机理进行了研究。根据SF6气体与电子各种相互碰撞过程的碰撞截面、电子能量阈值和各反应过程的速率常数数据，找出了影响F原子产出的重要过程。以SF6、D2为工作介质，根据非链式脉冲DF激光器的反应机理，采用速率方程理论，建立了非链式脉冲DF激光器动力学模型。采用Runge-Kutta法对该模型进行数值计算，得到了腔内各组分粒子数密度随时间的变化关系及DF分子各振动能级辐射跃迁激射光子情况。进而运用该模型研究了工作气体比例和输出镜反射率对DF激光器腔内光子数密度、单脉冲能量、脉冲宽度和输出功率的影响，得到了最佳气体比例和最佳输出镜反射率参数。搭建了非链式脉冲DF激光实验平台，研究了工作气体比例、总气压、充电电压和输出镜反射率对放电引发非链式脉冲DF激光器输出能量的影响。实验发现SF6与D2的最佳比例为10:1，最佳输出镜反射率为30%，上述实验结果与动力学模型模拟结果一致。在最佳工作条件下（SF6:D2=10:1，R=30%），充电电压为39kV时，激光单脉冲输出能量达到最大值4.95J，此时激光脉冲宽度为148.8ns，峰值功率为33.27MW。对激光脉冲特性进行了测量，给出了激光脉冲特性与气体比例、总气压、充电电压及输出镜反射率之间的变化关系。使用DF激光谱线分析仪对激光输出谱线进行了测量，得到了20条P支跃迁谱线，激光能量集中在v=2振动能级上。此外，采用烧蚀光斑法对稳腔结构的激光光斑进行了测量，得到DF激光近、远场发散角分别为1mrad和6mrad，在相同条件下，采用非稳腔可将激光光束远场发散角压缩到1.2mrad。; Deuterium fluoride (DF) laser，based on chemical reactions, radiates in the spectral range 3.5~4.2μm, which is the infrared atmospheric transparency window covering the absorption peaks of many atoms and molecules, so this laser has significant applications in many fields such as spectroscopy, laser radar transmitters, laser ranging, atmospheric monitoring, military, etc. Compared with traditional chain DF laser, non-chain pulsed DF laser has no risk of corrosion and explosion. Besides, it has other advantages, such as compact structure, easy operation, good beam quality, high peak power, high energy, etc. Non-chain DF laser becomes more attractive due to all these advantages recently. The mechanism of non-chain pulsed electric-discharge DF laser is studied theoretically and experimentally in this paper. According to the impact cross sections, threshold electron energy and rate coefficients of different impact interactions between SF6 and electrons, the important processes which affect the generation of F atoms are found. With SF6-D2 as gas medium, According to the reaction mechanism in non-chain pulsed DF laser, a dynamical model for this laser is presented by using rate equations theory. Through solving this model with Runge-Kutta method, the dependence of species concentration in laser cavity on time and the photons radiation by different vibrational level of excited state DF molecules are obtained. Then the effects of the working gas ratio and the reflectance of output mirror on photon number density, single pulse energy, pulse width, and output power are studied with this model. The optimum parameters of the working gas ratio and the reflectance of output mirror are attained based on the theory calculation. The experiment platform of non-chain pulsed DF laser is built, on which the influences of the ratio and total pressure of working gas, the charging voltage and the reflectance of output mirror on the output energy of non-chain pulsed DF laser are investigated. The results show that the optimum ratio of SF6-D2 ¬and the reflectance of output mirror, respectively, are 10:1 and 30%, which agree well with the theoretical calculation. The maximum single pulse energy of 4.95J, pulse duration of 148.8ns, and peak power of 33.27MW are achieved under the best working conditions (SF6:D2=10:1, R=30%) when the charging voltage is 39kV. The influences of the mixture ratio, total pressure, charging voltage and the reflectance of output mirror on impulse characteristics of non-chain DF laser are researched. By using the DF laser spectrum analyzer to measure the output spectrum of DF laser, 20 P-branch transition lines are attained, which the laser energy concentrates on v=2 vibration level. Besides, by measuring laser spot with the laser ablation method, the laser beam divergence angles of 1mrad and 6mrad in near field and far field respectively are attained. By replacing the resonator with a non-stable optical resonator, the far field laser beam divergence angle can be compressed to 1.2mrad in the same experimental conditions.
语种	中文
文献类型	学位论文
条目标识符	http://ir.ciomp.ac.cn/handle/181722/41458
专题	中科院长春光机所知识产出
推荐引用方式 GB/T 7714	阮鹏. 放电引发非链式脉冲DF激光机理研究[D]. 中国科学院大学,2014.

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