分子体系在等离子增强激光场中的高次谐波研究
时间:2019-03-08 17:16 来源:毕业论文 作者:毕业论文 点击:次
| 摘要本文阐述了高次谐波的研究背景、意义、理论模型，介绍了等离子体应用于高次谐波产生的发展现状以及分子高次谐波的相关应用。用纳米尖端实现激光场强度的非均匀分布对扩展高次谐波的截止区有着非常重要的作用，但是对于分子体系的相关研究还比较缺乏。本文通过解含时薛定谔方程，提出一个分别在对称的和非对称空间非均匀激光场中具有大核间距的H2+的高次谐波产生的理论研究，分析了分子体系与等离子体增强激光场相互作用产生的高次谐波特性。研究发现，在两种情况下，高次谐波谱第二平台都出现了最小值，并且最小值的位置不同。给出的解释是两中心干涉效应导致了最小值的出现，而位置的不同是由于原子核周围波包边界处不同激光场的影响。33644 关键词 高次谐波；分子体系；含时量子波包；强激光场；等离子共振增强；阿秒脉冲 毕业论文设计说明书外文摘要 Title Investigation of High-Order Harmonic Generation of Molecular System Exposed to Plasmon-Enhanced Laser Field Abstract The present thesis describes the research background, significance and theoretical model of high-order harmonic generation (HHG). It gives a brief introduction to the development status of using plasma in HHG and the relevant applications about HHG from molecules. Using nano-tip to achieve a non-uniform distribution of laser field strength plays a very important role in extending the cutoff of high-order harmonics. However, the relevant research for molecular systems is still relatively scarce. By solving the time-dependent Schrödinger equation, a theoretical investigation of HHG from H2+ with large internuclear distance in both symmetric spatially nonhomogeneous laser fields (SSNLF) and asymmetric spatially nonhomogeneous laser fields (ASNLF) is presented in this thesis. Characteristics of harmonics were analyzed, which is generated by the interaction between molecular system and plasma-enhanced laser field.It is found that the minimum in the second platform of high-order harmonic spectrum emerges in both cases and the locations of the minima are different. The emergence of minimum was attributed to two-center interference. Influence of different laser field on the wave packets bounded around the nuclear is responsible for the different location. Keywords High-order harmonic generation; Molecular system; Time-dependent quantum wave packet; Intense laser fields; Plasmon resonance enhancement; Attosecond pulse 目 次 1 绪论 1 1.1 高次谐波研究背景及意义 1 1.2 高次谐波研究进展及现状 4 1.3 论文主要工作及章节安排 8 2 高次谐波产生的理论模型 9 2.1 电离机制 9 2.2 三步模型10 2.3求解含时薛定谔方程与强场近似模型11 2.4分子的高次谐波发射机制12 3 LZH-DICP程序进行数值模拟计算14 3.1 LZH-DICP程序14 3.2 获得初始波包15 3.3 实时传播15 4 计算结果及分析17 4.1 对称和非对称空间非均匀激光场中H2+的高次谐波谱17 4.2 H2+高次谐波谱中的干涉极小现象18 结论 22 致谢 23 参考文献24 1 绪论 1.1 高次谐波研究背景及意义 1960年，T．H．Maiman发明了世界上第一台激光器。由此开始，激光技术的发展就一直朝着脉冲宽度更窄和脉冲强度更强的目标不断努力(如图1-1和图1-2) [1]。凭借亮度高、相干性强以及方向性好等优点，激光迅速在科研和生产中获得越来越广泛的应用。 (责任编辑：qin) |