高功率激光作用水介质的电离性质研究
毕业论文关键词 激光物理；光学击穿；水；脉冲激光；电子密度 Title Ionization Properties of high-power laser interaction with aqueous medium Abstract The applications and the main mechanism of high-power laser interaction with aqueous medium are described in this thesis. Latest progress and developments in this field are discussed as well. To calculate the irradiance threshold for laser-induced breakdown of water, two models are introduced. The rate equations contain two or more ionization mechanisms are created by using rate equation model in laser-induced breakdown, and we also discuss the main ionization mechanism and influence factors and analyze the relationship between the laser breakdown threshold and laser parameters, and compare the calculation results to the experiment results. For nanosecond laser pulses in distilled water, the generation of free electrons water is initiated by multiphoton ionization but then dominated by cascade ionization. For shorter laser pulses, multiphoton ionization is the dominated mechanism, and the collisions and recombination effect can influence the plasma density. Besides, the breakdown threshold for the near infrared laser is more dependent on the initial electrons. Keywords Laser physics, optical breakdown, water, laser pulses, electron density
目录
1绪论3
1.1研究背景.3
1.2研究意义.3
1.3研究进展.4
2国内外最新进展和动态..5
2.1国内外理论研究.5
2.2国内外实验研究.5
2.3医疗物理领域的应用和研究5
3激光诱导液体介质击穿的光学模型.7
3.1液体介质光学击穿现象.7
3.2光学击穿速率方程..8
3.3液体中光学击穿的简化模型9
4实际击穿阈值的确定12
4.3短激光脉冲条件12
5自由电子速率方程模型.14
5.1纯水介质中的计算.14
5.2含杂水中的计算14
5.3程序设计思想..14
6激光诱导水击穿阈值的计算和分析16
7结论..20
8总结与展望..21
8.1毕业设计工作总结.21
8.2激光作用水介质的发展21
致谢23
参考文献.24
附录A自由电子密度计算程序..28
1 绪论 1.1 研究背景 在激光学科的基础研究上，物质与激光相互作用的机理及过程一直是研究人员非常感兴趣的研究话题。在此前ᨀ下，又分为激光与气态、固态以及液态的相互作用等分支。其中，在与气态和固态物质上，国内研究方面已经有了长足的发展，理论也较为完善，应用在激光加工和激光武器等方面[1]。 与此同时，在液态物质与激光相互作用方面一直没有发展到与前两方面相似程度的地步，但液态物质的研究又是十分重要的。在此基础上，应先了解激光与液态物质相互作用的机制，例如在医学领域中激光与生物组织相互作用的应用，涉及到生物手术后激光诱导液体产生的空泡造成的影响，都是在当前十分值得关注的领域和项目[1]。
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