高次谐波产生及其特性的研究
文献类型：学位论文
| 作者 | 苗境 |
| 学位类别 | 博士 |
| 答辩日期 | 2014 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 曾志男 |
| 关键词 | 高次谐波产生 电子轨道 啁啾偏振门 阿秒脉冲 电子超快动力学 |
| 其他题名 | study on high-order harmonic generation and its speciallity |
| 中文摘要 | 研究超强激光脉冲与原子分子相互作用过程是近些年来一门发展很快的研究课题。强场脉冲与物质相互作用产生的高阶非线性效应是强场物理研究的主要任务，也是研究强场物理的基础。高次谐波作为强场物理中一种高阶非线性效应，是产生极紫外辐射的一种方法，也是合成阿秒脉冲用于研究超快电子动力学的重要手段。分子与原子相比，由于结构复杂、具有多个原子核， 能够展现出比原子中更多的新的强场效应，因此也成为了目前强场物理研究的前沿。 本文的主要工作就是研究高次谐波的产生这一课题，研究产生了具有新的特性的高次谐波信号，并且对分子内的高次谐波产生过程做了理论的分析。主要结果和创新点包括： 1. 提出了利用线性啁啾偏振门产生可调谐的双阿秒脉冲的新方案。理论上研究了在两束垂直偏振的含有线性啁啾的激光脉冲作用下的高次谐波产生。由于这种新的偏振门中的时间窗是由两个可以随着驱动光场延时变化而改变位置的时间窗构成的，因此，在这种方案中可以产生两个延时可以调节的XUV脉冲。这种XUV光源可以为阿秒泵浦-阿秒探测技术提供很理想的相干光源。 2. 实验上利用三色驱动场在气体中产生了一个单个高次谐波信号，谐波信号与其相邻信号的对比度高于10，产生的高次谐波信号具有高的单色性。理论上解释了三色场情况下，由于存在着原子内相位匹配的效应，对于目标信号各个轨道的相位变化被极大的抑制在π范围内，而其他级次的效果不明显。这种极紫外光源可以作为一种单色的相干源来应用。 3. 利用两束互相垂直偏振的800nm的长脉冲驱动光源实现了线性啁啾偏振门，实验中观察到了在这种偏振门的作用下，某些级次高次谐波谱带宽可以得到2倍以上展宽。 4. 通过MO-ADK模型和分子强场近似下，以Lewenstein模型为基础求解了激光脉冲与分子相互作用下的高次谐波产生。理论计算了在双色场作用下氮气分子HOMO轨道和HOMO-1轨道中的高次谐波随驱动电场与分子轴之间夹角的变化。指出了氮气分子不同轨道在随着激光脉冲电场与分子轴夹角变化就有不同的特性，为以后研究分子取向下高次谐波提供基础。 |
| 英文摘要 | The study of super intense laser-matter interactions process is one of the most rapidly developing topics. The high-order non-linear effects are the basis and major task in the field of intense laser-matter interactions. The high-order harmonic generation (HHG) as one high-order non-linear effects in the field of strong-field physics is promising scheme to generate a extreme ultraviolet (XUV) emission and an effective way to synthesis the attosecond pulse which can be used to probe the ultrafast electron dynamics. Comparing with the atom, the molecule can reveal more complexity in the strong-field process due to complex structure and more uncleus. The laser-molecule interactions has been the front in strong field. In this letter, the chief work is studying of high-order harmonic generation, finding the new feature in harmonic and analyzing the HHG in molecule in theory. The main results and innovations include: 1.We propose a new scheme to generate two attosecond pulses with tunable delay using orthogonally-polarized chirped laser pulses. We investigate theoretically the HHG by this polarized chirp laser polarizing gating. In this scheme, we show that such generating field has a specific temporal variation of the ellipticity which provides generation of two XUV attosecond pulses with tunable delay between them. This kind of XUV source could be used to provide a coherent light for the attosecond-pump and attosecond-probe technology. 2.An isolated and highly monochromatic high-order harmonic is achieved in argon based on a multi-color laser field that consists of the fundamental, second and third harmonic fields of a femtosecond Ti:sapphire laser. By controlling the relative phase between the fields and controlling the gas pressure, the 18th harmonic is greatly enhanced alone while the adjacent harmonics are suppressed, whose contrast ratio is improved by more than 10 times. Through the theoretical research, we find the inter-atomic phase matching make the most important contribution. This scheme provides a new means to generating a coherent and highly monochromatic soft X-ray source with a greatly enhanced brightness. 3.We observe the harmonic spectra bandwidth broadening with the polarization gating in experiment. The polarization gating is formed by two orthogonally-polarized linearly chirped multi-cycle 800nm laser pulses. Some spectral bandwidths of the harmonics can be broadened by more than two times. 4.We obtain the dipole moment in the molecule following the Lewenstein model of harmonic generation in atoms by the MO-ADK model and MO-SFA model. We calculate the harmonic generation in the HOMO orbit and HOMO-1 orbit of nitrogen molecule versus the angle between the electric field and molecular axial. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15866]  |
| 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 | 苗境. 高次谐波产生及其特性的研究[D]. 中国科学院上海光学精密机械研究所. 2014. |
入库方式： OAI收割
来源：上海光学精密机械研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。