| 题名 | 拍瓦激光在线焦斑检测技术的研究 |
| 作者 | 金博 |
| 学位类别 | 硕士 |
| 答辩日期 | 2013 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 赵东峰 |
| 关键词 | 拍瓦激光 在线焦斑检测 离轴抛物面镜 光栅拼接 |
| 其他题名 | Study on Pettwatt Laser On-shot Focal-spot Diagnostics |
| 中文摘要 | 在阿秒科学、高能束线和超强场科学等研究领域，即探索激光与物质相互作用方面，需要具有拍瓦量级（10E15W）峰值功率的激光驱动装置，这就需要在现有激光技术基础上建立超高峰值功率激光装置。本文在超高峰值功率激光装置宽带放大技术基础上，开展在线焦斑形态检测的研究与实验判断，目的在于提供可适用于工程要求的技术，其主要内容如下： 首先，本文主要介绍了引起拍瓦激光焦斑形波前畸变源，包括激光光束质量，离轴抛物面镜（OAP）的成像特性与聚焦误差分析，大口径光栅拼接对焦斑形态的影响。其中，聚焦元件OAP是影响焦斑形态最重要的因素之一，这里以OAP的几何成像特性为出发点，讨论了两方面问题：第一，沿主光线离焦的一平面上的光线投影成像；第二，在几何光学范畴内，讨论了离焦平面上的光强分布情况：理想平面波入射时会使平面上的光强分布呈现不均匀性，而高斯光束的入射则能削弱这种不均匀。接下来，基于OAP的几何成像特性，讨论了具体的实验用OAP的数学模型。基于此模型，提出了具体的设计参数与调节量的要求。接下来讨论了光栅拼接技术对焦斑形态带来的影响，分为单块光栅与1×3光栅拼接两种情况。首先，在单块光栅的条件下，光栅的空间6自由度分别对聚焦焦斑产生不同的影响，其中前后位移的影响灵敏度最高。而1×3光栅拼接的情况下会对焦斑产生分裂效应。这里针对此种情况，设计了专门的实验来对光栅的稳定性，焦斑分裂，能量分布进行分析。 通过对拍瓦激光焦斑形波前畸变源的分析与实际工程的需要，间接的焦斑检测方法是必然的。针对间接测量的固有误差，必须以靶室内的焦斑处为基准，对采样激光进行波前的校正，矫正的关键在于两方面：首先必须精确测量出光束通过缩束器后的口径大小；再次，(a)采样激光由分束镜传播到哈特曼传感器所产生的畸变必须减去，(b)主激光由分束镜传播到离轴抛物面镜乃至最终聚焦所产生的畸变必须加上。将(a)与(b)的差别记作固有误差ΔW，ΔW将在计算最终焦斑能量分布前事先校正。对于固有误差的测量，这里也给出了具体测量方法与具体的光路准直方法。基于以上方案，文章最后通过对比试验结果的分析，固有误差的测量与补偿理论有效的提高了在线焦斑检测方法的精度在实验平台上得到了证明，测量精度达到了70%。 |
| 英文摘要 | In the areas of attosecond science, high-energy beam lines and ultra-high field science research, namely exploring the laser matter interaction, the petawatt class (10E15W)laser facility is needed, so that ultra-short, ultra-high peak power laser device is required to be established on the basis of existing laser technology. This article, based on the technology of broadband amplification in ultra-short, ultra-high peak power laser device, is to carry out research and experiments to determine specific form of on-shot focal spot diagnostics for pettwatt laser device and to further provide particular technology applied to engineering requirements. The main contents of this article are as follows: First，this article mainly stands as pettwatt laser beam focal spot aberration caused by the distribution of the wavefront distortion, including laser beam quality criteria, the off-axis parabolic mirror (OAP) imaging characteristics and the analysis of focus error, large-aperture gating tiling by interferometry. The focusing element OAP is one of the most important factors that affects the focal spot characterization. Based on the geometry of the imaging characteristics of the OAP as a starting point, we are to discuss two aspects: first, the imaging theory in the focal plane along the main beam; Second, focal spot intensity distribution in the domain of geometrical optics: incident ideal plane wave will make the plane light intensity distribution show a state of non-uniformity, and incident Gaussian beam can undermine this uneven. Next, based on the geometry of the imaging characteristics of the OAP, we discussed the mathematical model of the specific experimental OAP. Based on this model, the specific requirements of the design parameters and the adjustment amount is presented. Next, we discussed the impact of large-aperture grating tilling techniques on focal spot characterization, and it is divided into two cases: one single block of the grating and 1 × 3 style. First, under the conditions of the single block situation, 6 DOFs respectively produces different effects on the focal spot, wherein the piston error shows highest sensitivity. Case of 1 × 3 grating tilling would produce focal spot splitting effect. In such cases, we have designed special experiments on the stability of the grating, the focal spot division, energy distribution analysis, and finally got the quantitative relationship of the focal spot splitting degree of piston error. Through analyses of distribution of the wavefront distortion and the actual needs of the project, the indirect focal spot detection method is inevitable. The intrinsic focal spot diagnostics, like the other on-shot laser diagnostics, measures a lower-energy sample of the main beam that is attenuated and down-collimated to a more convenient beam size. Careful calibration is necessary to ensure that measurements made on the sample beam reflect the main beam at focus. Therefore, a critical part of the method is the cross-calibration of the wave front sensor measurements to a spherical reference surface centered on the target location, from which the optical fields are numerically propagated to the focal spot location. To gain this instinct wavefront error,.(a) sample beam aberrations that are artifacts in the on-shot measurement that must be subtracted and; (b) aberrations in the main beam path that are after the diagnostic mirror and so must be added to the on-shot measurement. This difference, the transfer wavefront (ΔW)， is applied to correct the on-shot measurement before calculating the focal spot. For the measurement of the transfer wavefront, there also presents a specific method and optical alignment. Finally, by comparing the test results and the measurement results, measurement and compensation theory of the inherent errors effectively improve the accuracy of the on-shot focal-spot diagnostics has been proved, accuracy of measurement is 70%. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16753]  |
| 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 | 金博. 拍瓦激光在线焦斑检测技术的研究[D]. 中国科学院上海光学精密机械研究所. 2013. |
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