相对论飞秒激光与自由电子及等离子体相互作用产生阿秒相干X射线源的研究
文献类型：学位论文
| 作者 | 刘丽 |
| 学位类别 | 博士 |
| 答辩日期 | 2010 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 李儒新 ; 刘建胜 |
| 关键词 | 高次谐波 超短超强激光 阿秒脉冲 载波包络相位 汤姆逊散射 粒子模拟 |
| 其他题名 | Study on the generation of attosecond coherent X-ray source from relativistic femtosecond laser interaction with free electrons and plasmas |
| 中文摘要 | 超强超快激光技术的发展拓展了人们对物理世界的认知。就时间尺度而言，人们的微观认知已经进入阿秒 (10-18秒) 量级。阿秒科学使人们在更精细的时间和空间尺度上研究电子和分子的动力学成为可能。由于电子壳层的动力学尺度也为阿秒量级，因此阿秒脉冲，特别是单个阿秒脉冲作为高分辨率的探针，将在物理，生物，材料，化学等方面有着广泛且重要的应用。 阿秒脉冲产生的基础是激光与物质相互作用中的非线性现象——高次谐波。激光技术的发展使得激光的聚焦强度已经达到1022-1023 W/cm2，进入了强相对论范畴。这为高次谐波/阿秒脉冲的产生提供了有力的工具。阿秒脉冲的产生有三种途径：(1) 激光与气体原子相互作用产生高次谐波；(2) 激光与等离子体相互作用产生高次谐波；(3) 基于激光与自由电子相互作用的非线性 Thomson 散射产生高次谐波。 本论文工作瞄准获得阿秒超快脉冲这一前沿课题，重点研究了在激光与自由电子及等离子体相互作用中控制产生单个阿秒脉冲等基本物理问题，主要工作和成果包括以下几个方面： 1. 在激光与自由电子相互作用中，提出了对撞激光入射自由电子产生单个阿秒脉冲的方案，分析了单个阿秒脉冲产生的条件，分别研究了载波包络相位对线偏振激光入射和圆偏振激光入射产生单个阿秒脉冲的影响。结果表明仅在圆偏振激光作为驱动脉冲的情况下，才能够产生稳定的单个阿秒脉冲。对双脉冲入射和单脉冲入射进行对比研究，表明在两种偏振光入射的情况下，双脉冲作为驱动脉冲时所得到的辐射可以大大地增强。分别分析了双脉冲对射和单脉冲入射时辐射的角分布特性，并且对线偏振激光入射的情况，比较分析了双脉冲对射和单脉冲入射两种情况下电子在其运动面内辐射的角分布对称特性。 2. 在激光与等离子体相互作用中，研究了载波包络相位对利用偏振门的方法产生单个阿秒脉冲的影响。通过时频分析的方法，分析了单个阿秒脉冲产生的原因及载波包络相位对阿秒脉冲产生的影响，并利用振动镜面模型对载波包络相位的影响进行了物理上的分析。结果表明两种分析方法能够相互验证。稳定的载波包络相位对单个阿秒脉冲的产生是必要的。 3. 在实验研究激光与固体相互作用产生高次谐波方面，搭建了产生固体表面高次谐波的实验光路，并利用碳氢膜，铝等作为靶材料进行了打靶实验；观测到铝的特征谱线并利用其进行分析定标。利用可变形镜改善激光波前质量的实验，表明加入可变形镜可以降低波前的峰峰值，均方根差，使得波前的质量得到改善。等离子体镜实验表明经过等离子体镜后，激光的对比度得到了提高。 |
| 英文摘要 | The development of ultraintense and ultrashort laser technology extends our cognition of the physics world. As far as timescale is concerned, it has been pushed to the level of attosecond. Attosecond science makes the study of electron and molecule on ever-shorter time scale and spatial scale possible. Since the timescale of the dynamics in the electronic shell of atoms is on the attosecond scale, attosecond pulses, especially the single attosecond pulse as the highly time-resolved probe, will play the abroad and important role in the applications such as those encountered in the physical, biological, chemical, and material sciences. The generation of attosecond pulses is based on the nonlinear effect from interaction of laser and matter-high order harmonics. The laser intensity at the focus has been raised to 1022-1023 W/cm2, entering into the ultra relativistic regime through the recent advances in laser technology. This will provide the powerful tool for generating high order harmonics/attosecond pulses. There are three methods to generate attosecond pulses. The first one is the generation of high order harmonics from the interaction of laser and atoms; the second one is the generation of high order harmonics from the interaction of laser and plasmas instead of atoms; and the third one is the generation of high order harmonics based on the nonlinear Thomson scattering of intense laser pulses by free electrons. Aiming at how to generate the attosecond pulses, the generation of single attosecond pulses from the laser pulses interaction with free electrons and plasmas is the main subject of this Ph. D dissertation. The main results are listed as follows: 1. Single attosecond pulses generated via electron''s Thomson scattering of two counter-propagating laser pulses is proposed. The condition to generate a single attosecond pulses is analyzed and the influence of the carrier envelope phase (CEP) on the generation of single attosecond pulses is investigated respectively for linear and circular polarizations. Numerical results showed that using circularly polarized pulses can not only obtain a single attosecond pulse, but also make its generation avoid the influence of CEP. The radiation power obtained by using two counter-propagating pulses can be significantly enhanced in comparison with that obtained by using only one of these two pulses. In the case of linear polarization, the symmetrical characteristics of the radiation angular distributions are analyzed for two incident pulses and a single incident pulse, respectively. 2. The influence of the CEP of the driving laser pulse on the generation of single attosecond pulses from surface harmonics by using the polarization gating technique is investigated in detail. The influence is studied further by performing time-frequency analyses of the reflected electric fields. The physical origin of the influence of the CEP is explained in terms of the oscillating mirror model. These two kinds of analyses are in consistent with each other. It is shown that choosing the proper and stabilized CEP is essential for the generation of single attosecond pulses. 3. The preliminary experiments of the high harmonic generation from the interaction of femtosecond (fs) laser pulses with solid targets, eg., CH foils and Al blocks, have been carried out. The characteristic spectral lines of Al are observed and used to calibrate the harmonic spectra. The preliminary experiment on correcting the wavefront aberrations has shown the wavefront amplitude (P-V) and the root-mean-square error of the wavefront have been decreased after correction, thus the wavefront of the laser pulse has been optimized. The experiment of plasma mirror has shown that the contrast of the laser pulse has been increased after reflected by the plasma mirror. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15301]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 刘丽. 相对论飞秒激光与自由电子及等离子体相互作用产生阿秒相干X射线源的研究[D]. 中国科学院上海光学精密机械研究所. 2010. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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