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题名	高功率激光驱动器光束匀滑技术研究
作者	江秀娟
学位类别	博士
答辩日期	2007
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
关键词	高功率激光驱动器 靶面辐照均匀性 光谱色散平滑 透镜列阵
其他题名	Research on Beam Smoothing in High Power Laser Driver
中文摘要	本文调研了国际上现有的均匀辐照技术，在此基础上主要完成了以下工作： 1. 提出将LA和SSD相结合以改善激光等离子体实验中的靶面照明质量。通过LA可以在靶面获得边缘陡峭且没有旁瓣的准近场焦斑，不同子光束之间干涉所引起的细密条纹可以利用SSD技术消除。使靶面适当离开主聚焦透镜的焦面可以进一步降低焦斑内部中等空间尺度的强度调制，而且离焦量存在最佳值。初步实验结果与二维数值结果基本一致。 2. 提出采用软边LA和SSD来提高靶面辐照均匀性。利用软边LA无需离焦就可抑制衍射引起的中等空间尺度强度调制。二维数值计算结果显示，采用该联合技术可以获得边缘陡峭顶部平坦的焦斑，而且这种方案对入射光近场畸变有较大的宽容度。焦斑的均匀辐照程度受SSD和LA参数选取的影响，在做具体设计时要在焦斑均匀性与能量利用率之间取得合理的平衡。3. 分析了LA和SSD联合使用时靶面辐照均匀性对激光波长的依赖关系。使用长波长激光时，靶丸内部的热传导平滑非常有效，能把烧蚀面上的压力不均匀度降低到大约1%；而对于紫外的短波长激光，热传导区很窄，热传导平滑作用很小，SSD是主要的平滑机制。如果把LA、SSD和热传导平滑综合起来考虑，长波长激光仍然有利于在靶面产生均匀性较好的焦斑。 4. 在理论上研究了SSD单元对激光驱动器中光束传输特性的影响。经过光散后，光束衍射光斑变大，本身存在畸变的近场均匀性可能得到改善，远场光斑中心附近出现光强接近于均匀分布的区域。论文中还分析了SSD单元各主要元件参数对光束传输的影响，结果表明，在实际应用SSD时，要合理地选择元件参数以获得理想的光束传输效果。
英文摘要	Uniform on-target irradiation is demanded in inertial confinement fusion and its relative physics experiments, and the improvement of the uniformity has long been an important task in the research of high power laser driver. In this thesis, based on a comprehensive review on this field, the complete work is summarized below: 1. A scheme employing LA and SSD is presented to improve target illumination uniformity in laser produced plasmas. When the laser beam irradiates a LA system, a quasi-near-field pattern, of steeper edges and without side lobes, is obtained on the target. The fine stripes due to interference between different beamlets can much better be smoothed out when SSD is added. Moving the target slightly, from the exact focal plane of the principal focusing lens, can eliminate middle-scale-length intensity fluctuation in the pattern and thus improve its uniformity further. It is also evident that there exist optimal target moving distances. The two-dimensional simulations are in agreement with the experimental results.2. The two-dimensional performance of uniform irradiation on the target with the joint techniques of an edge-softened lens array and spectral dispersion is explored. A quasi-near-field target pattern is obtained by using a lens array. Softening the edges of lens elements, middle-scale intensity fluctuation in the pattern due to diffraction is reduced greatly. Two-dimensional theoretic results indicate that an excellently illuminated target spot of steeper edges and a flat top can be achieved with this combination, and LA is insensitive to the near-field large-scale nonuniformity, which makes this scheme a good candidate for uniform target illumination. The on-target irradiation is affected by the choices of parameters of the SSD and LA system, and balance between the uniformity and energy efficiency should be made to achieve the best performance. 3. It is investigated the wavelength dependence of the target irradiation uniformity in the scheme using LA and SSD. For a long wavelength laser, thermal conduction smoothing within the target is quite effective which can reduce the pressure nonuniformity on the ablation surface to around 1%, while for the ultraviolet laser of short wavelength, the thermal conduction zone is very narrow and the thermal smoothing doesn't work well, so SSD is the main smoothing mechanism. When LA, SSD and thermal smoothing are all taken into account, long wavelength laser will still produce better irradiation uniformity on the target.4. It is simulated numerically the transmission of beams phase modulated and spectrally dispersed by the unit for smoothing by spectral dispersion put in the laser driver. The results show that the diffraction spot of a spectrally dispersed beam becomes larger and its near-field uniformity is improved, while there exists area where the intensity is nearly even within the far-field spot. The effects of the main parameters of the electro-optic phase modulator and the grating in the unit on the diffraction characteristics of the beams are further discussed, and it is found that intensity modulation emerges in the far-field spot under some conditions.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15423]
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	江秀娟. 高功率激光驱动器光束匀滑技术研究[D]. 中国科学院上海光学精密机械研究所. 2007.

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