短脉冲激光参数精密测量技术
文献类型：学位论文
| 作者 | 欧阳小平 |
| 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 | 朱健强 |
| 关键词 | 激光参数测量 超短脉冲 信噪比 |
| 其他题名 | Laser Parameter Precise Diagnostics for Short Pulse |
| 中文摘要 | 本课题致力于百飞秒（fs）和皮秒（ps）量级超短脉冲激光参数的精密测量技术的研究工作，并针对快点火实验方案对点火激光驱动器的工程需求开展相应的预研工作。信噪比是超短脉冲激光的一项重要参数，过高的噪声会在靶丸上产生等离子体，使后续的主脉冲无法与靶丸相互作用。由于短脉冲激光的持续时间短于光电探测器的响应时间，因此只能采用自相关方法进行超短脉冲的时间特性检测。传统的自相关方法在超短脉冲的宽度测量中被广泛应用，本课题研究了自相关方法在超短脉冲信噪比精密测量中的应用。 首先分析了自相关过程的基本理论及利用晶体中的非线性效应实现自相关的物理过程，得出二阶自相关过程和三阶互相关过程中的信噪比测量结果等效于被测脉冲的信噪比这个重要结论。并以此为基础讨论了重复频率脉冲的信噪比测量系统动态范围的分析方法。在详细分析基本原理之后，开展了二阶自相关和三阶互相关原理下的重复频率信噪比测量实验研究。在重复频率脉冲的信噪比测量实验中还开展了信噪比测量系统的误差分析，掌握了分析判断信噪比测量过程中的误差来源并加以排除的方法，以及提高信噪比测量动态范围的关键技术，在国内首先实现了~108动态范围的信噪比测量。为了从一个简洁明了的角度来判断信噪比测量系统的动态范围，本课题还将0°反射镜后表面的的二次反射光形成的等间隔、等比例衰减的脉冲序列作为基准，在国际上首先开展了信噪比测量系统的动态范围标定方法的研究工作，并通过实验加以验证。 在重复频率信噪比测量系统的研究基础之上，本课题继续开展了单次脉冲信噪比测量系统的研究工作，以满足大型超短脉冲激光系统的极低重复频率脉冲的信噪比测量要求。单次脉冲信噪比测量的基本原理，也是三阶自相关方法，但高动态范围和主脉冲之前百皮秒的时间扫描范围这两个要求，提高了其技术难度。脉冲复制器能够兼容高动态范围和大的时间扫描范围，实现单次信噪比测量的基本需求。为了弥补其采样点间距偏大，有可能遗漏某些脉宽极窄的噪声的局限性，本课题提出了脉冲复制器的改进方法，将互相关过程中的点光束改为线光束，从而将扫描脉冲的多点修改为多窗口扫描，并通过多窗口的拼接提高单次脉冲信噪比测量的准确性。 为了开展短脉冲激光参数的精密测量工作，本课题还开展了拍瓦激光装置终端的参数测量单元的研究工作，通过分析大能量皮秒脉冲激光的取样、传输、缩束过程，以及相应的能量、脉冲宽度、远场测量模块的工作性能，确定了拍瓦激光装置中的参数测量系统的技术路线和技术方案。 |
| 英文摘要 | This article endeavors research of laser parameter precise diagnostics technology for short pulse such as ~100fs and ~1ps, and takes an initial investigation for fast ignition project’s requirement about ignition laser driver. Pulse contrast is an important parameter in ultra short pulses. And intense noise will generate plasma on target, which block sequent main pulse to react with target.Autocorrelation is just the method to diagnose short pulse’s temporal characters, for short pulse’s duration is much shorter than response time of photo-electronics detectors. This article has researched autocorrelation’s application in short pulse contrast measurement, although traditional autocorrelation is widely used in short pulse width measurement. This article commences with analysis of autocorrelation’s basic principle and physical procession that using nonlinear phenomena in crystal to realize autocorrelation, then derives an important conclusion that pulse contrast measurements of 2nd order autocorrelation and 3rd order cross-correlation equal the one of measuring pulse. Estimation of a pulse contrast measurement system is also discussed based on former conclusion.After detailed analysis of related principle, we take up a series experiments of repetitive pulses’ contrast measurement under 2nd order autocorrelation and 3rd order cross-correlation. Tolerance is also considered in pulse contrast measurement for repetitive pulses, which helps to find noise’s source and ways to eliminate it. After above research we have gripped the keys limiting the dynamic range of pulse contrast measurement, and achieve a high dynamic range with ~108 in pulse contrast measurement in our country. In order to testify a pulse contrast measurement’s dynamic range in a simple and clear way, this article uses a series of pulses with equal intervals and equal ratios of intensity as a criterion, which reflected from back surface of a 0°reflector, and first discuss the calibration of pulse contras measurement and verify it by experiments in the world. With a successful research in repetitive pulses’ contrast measurement, this article goes on to explore pulse contrast measurement for single shot pulse to fulfill the requirement of large short laser system with very lower repetitive outputs. The principle of single shot pulse contrast measurement is also based on 3rd order cross-correlation, but more hard to realize high dynamic range and long scan range at the same time. Pulse replicators can achieve both high dynamic range and long scan range, and satisfy single shot pulse contrast measurement. After all an update method for pulse replicators is provided to amend its defect which has intervals between sample points which may omit some ultra short noise. Our update method substitutes line beam for spot beam, thus scanning spots replaced by scanning windows, so a more true measurement is obtained by titling these windows. For short pulse contrast precise diagnostics, this article also make an effort to the research of parameter diagnostics unit at the end of Peta-Watt laser facility. That diagnostics’ technical method and blue print for Peta-Watt laser has designed after detailed analysis on Peta-Watt laser’s sampling, propagation, down-collimator, and related modules of energy, pulse width, far-field. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15283]  |
| 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 | 欧阳小平. 短脉冲激光参数精密测量技术[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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