皮秒拍瓦前端OPCPA的工程设计研究
文献类型：学位论文
| 作者 | 王艳海 |
| 学位类别 | 博士 |
| 答辩日期 | 2009 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 林尊琪 ; 李学春 |
| 关键词 | 光参量啁啾脉冲放大 千焦尔钕玻璃拍瓦激光器 信噪比 光束质量 惯性约束核聚变 激光脉冲时间整形 光谱整形 |
| 其他题名 | Engineering Design Research on OPCPA for the Front End of Picosecond-Petawatt-class Lasers |
| 中文摘要 | 与传统激光再生放大和多程放大原理比较，光参量啁啾脉冲放大技术(OPCPA)，具有诸多优点，如高增益、高稳定性、工作介质短、大带宽、高脉冲对比度、高光束质量、低热沉积等，对于获得更短的激光脉冲、更高的聚焦强度和更高的信噪比十分有利。已建和在建的钕玻璃拍瓦皮秒或亚皮秒激光装置大多在前端采用了两级或三级OPCPA放大代替再生放大级。本文围绕神光II千焦尔钕玻璃皮秒拍瓦激光器升级项目的前端OPCPA系统开展了以下工作： 1. 结合分步傅立叶和四阶龙格-库塔算法，编写了模拟OPCPA的数值算法程序，数值模拟研究了前端OPCPA的稳定性和转换效率问题，数值模拟结果表明，当泵浦光脉冲时间波形为超高斯分布，并且OPA工作在接近饱和状态时，空间和时间增益窄化效应可以忽略；当OPCPA分为高增益放大和功率放大两级放大，且第一级高增益OPA工作在过饱和状态时，第二级功率放大OPA有一个能量转换效率比较高、光斑强度调制较小的稳定工作区。 2. 对前端OPCPA信噪比进行了优化设计分析。结合快速傅立叶变换算法和宽带激光传输放大理论，编写了一维模拟超短脉冲展宽与压缩、光参量放大和啁啾激光脉冲传输放大的程序，利用该程序数值模拟研究了超短脉冲展宽、光参量放大过程中导致再压缩脉冲信噪比下降的问题。 3. 提出了一种OPA非共线优化结构，即使泵浦光存在严重的波前畸变，信号光仍能保持良好的光束质量。理论和数值研究了泵浦光存在严重波前畸变情况下OPCPA输出光束质量问题，即泵浦光波前畸变与信号光振幅耦合，泵浦光-信号光畸变波前传递，导致信号光近场和远场光束质量变差等问题进行了详细的研究。 4. 结合神光II拍瓦升级装置系统特征，数值模拟研究了超短脉冲从展宽、到光参量放大、再到后续钕玻璃介质放大过程中的脉冲的能量增益、时间波形、光谱形状的变化，以及在钕玻璃放大介质中传输放大过程中的增益窄化、增益饱和和自相位调制等问题。数值模拟结果表明，神光II第九路激光放大器系统光路无须做大的改动，即可满足输出激光脉冲能量不小于2000J、脉宽可压缩至1ps的工作能力。 5. 详细讨论了利用基于ACSL的集成电光波导调制的激光脉冲时间整形技术对啁啾展宽激光脉冲进行光谱整形的问题。理论和实验研究了基于ACSL电脉冲发生器的窄带激光脉冲时间整形系统，该系统可以实现窄带激光脉冲时间灵活整形，克服增益饱和效应，实现ICF激光驱动器特定时间形状的激光脉冲输出。同样，SG-II PW激光器前端OPCPA的泵浦激光脉冲时间波形设计也是基于此技术的。 |
| 英文摘要 | Compared with classical regenerative laser amplification and the principle of multi-pass amplification, OPCPA has a number of advantages, such as high gain, high stability, short gain medium, large gain bandwidth, high pulse contrast, high beam quality and low heat deposition, and this is helpful to achieve the laser pulses with shorter temporal duration, higher focusing intensity and higher signal-noise ration. Instead of regenerative amplification, two- or three-stage OPCPA system are used for the front end in most of large, petawatt-class Nd:glass laser systems, which have been built or are under construction. This thesis mainly focusing on the OPCPA system for the front end of kilo-joule, petawatt-class Nd:glass laser system for the SG-II PW upgrade facility: 1. Combining split-step Fourier technique and fourth-order Runge-Kutta algorithm, we wrote a three-dimensional program modeling OPCPA process. The stability and parametric conversion efficiency of OPCPA system were numerically investigated, and the results have shown that for OPCPA systems that operate in high-saturation, the spatial and temporal gain-narrowing effect can be neglected with high-order super-Gaussian pump shapes. Additional simulations have shown that for OPCPA systems consisting of high-gain preamplifier and power amplifier, the preamplifier had to be operated farther into reconversion in order to obtain high efficiency, high beam quality and stable output from the power amplifier. 2. An optimization of the signal-noise-ration of OPCPA system was made. Combining fast Fourier transform and the theory of propagation and amplification of broadband laser pulses, we wrote a one-dimension program to model the broadening and recompression of the ultrashort laser pulse, optical parametric amplification and the propagation and amplification of the chirped pulse. The degradation of the recompressed pulse was investigated numerically in the broadening, and OPA process. 3. An optimization of noncollinear OPA geometry was proposed to maintain the good beam quality even if the wavefront of pump pulse is distorted seriously. The output beam quality of OPCPA system when the wavefront of pump laser pulse was distorted seriously were investigated theoretical and numerically. The degradation of the near-field and far field beam quality of the signal, induced by Pump-phase- to-signal-amplitude coupling and pump aberrated phase transfer onto the signal, was investigated in detail. 4. Combining the system characteristics of the SG-II PW upgrade facility, we performed a systematic investigation of the energy gain, the changes of the temporal and spectral profiles in the broadening process, OPA and the following amplification in Nd:glass amplifier. Besides, gain narrowing, gain saturation, and self-phase modulation in the Nd:glass amplifier, were also modeled in detail. The numerical results have shown that the amplification chain of the SG-II ninth beam with no need of doing too much adjustment is capable of providing laser pulses with 2000J energy and less than 1 ps duration. 5. The spectral shaping method for the chirped pulse, based on integrated waveguide modulator driven by an aperture-coupled-stripline (ACSL) electrical-waveform generator, was described and numerically investigated in detail. An optical narrow- pulse-shaping technique using ACSL electrical-waveform generator has been investigated theoretically and experimentally. This system is capable of producing temporally shaped optical pulse to compensate the effect of gain saturation and making ICF laser facility export laser pulses with specially temporal profiles. The design of pump temporal profiles for the OPCPA front end of SG-II PW facility is also based on this technique. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15279]  |
| 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 | 王艳海. 皮秒拍瓦前端OPCPA的工程设计研究[D]. 中国科学院上海光学精密机械研究所. 2009. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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