【作者】 郑建洲；

【导师】 于清旭；

【作者基本信息】 大连理工大学 ， 光学工程， 2011， 博士

【摘要】 在惯性约束聚变(ICF)等精密物理实验研究中对高功率激光靶面辐照的均匀性提出了苛刻的要求。实现靶面均匀辐照是实验成败的关键因素,也是当前该领域中前沿性课题,具有重要的学术价值和实际意义。本论文主要研究在强激光技术中对靶面均匀辐照问题有重要意义的列阵式均匀辐照光学系统,取得了以下主要结果：1.首次提出了正交柱透镜列阵光学系统(OCLA),应用标量衍射积分理论和傍轴矩阵光学的方法,给出了系统的设计原理和OCLA系统远场和准远场光强分布的解析表达式,并对OCLA系统的匀滑特性进行了详细的数值模拟和优化设计。提出了应用离焦打靶和消衍射方法抑制OCLA系统的大尺度不均匀性。2.提出了两种焦斑可调的列阵式点聚焦系统,①焦斑可调的透镜列阵均匀辐照光学系统,②可变焦正交柱透镜列阵均匀辐照光学系统。应用矩阵光学和广义衍射积分理论分析了两变焦均匀辐照光学系统的工作原理和优化设计的参数。对两可变焦列阵式均匀辐照光学系统的数值模拟和Zemax光学软件的检验,证实了其匀滑的效果。3.通过理论和实验详细研究了正交光楔列阵(CSWA)聚焦系统的小尺度不均匀性的变化规律。根据波动物理光学,首次推导出了CSWA系统的多光束干涉条纹主极大和两相邻主极大间的次极大间距公式,应用柯林斯公式和ABCD传输矩阵理论由数值模拟计算证明了CSWA的小尺度不均匀性的变化规律。对两种抑制CSWA系统小尺度不均匀性(the SSRNU)的方法楔角偏差和离焦打靶建设进行了理论和实验研究,两者符合的非好。给出了楔角偏差和离焦量的最佳设计参数。4.应用偏振控制板(PCP)和正交柱透镜列阵结合的方法抑制靶面的小尺度辐照不均匀性。应用物理光学软件GLAD对该方案的匀滑效果进行了详细的三维数值模拟,并通过适当离焦,均匀度和能量利用率都可达到最佳值。5.基于部分相干光的传输规律和广义衍射积分理论,由高斯—谢尔模型(GSM)光束描述准单色部分空间相干光,建立了部分相干光PCL通过透镜列阵系统光强分布的理论模型以降低焦斑的小尺度(高阶模)不均匀性,通过详细的三维数值计算分析表明,与完全相干光通过该匀滑系统时相比更能显示该方案匀滑效果的优越性。如果考虑横向热平滑效果以及靶面适当离焦时,靶面上的高频空间光强调制可以得到进一步的抑制,可得到最好的辐照均匀性和能量利用率。更多还原

【Abstract】 In the sophisticated physical experimental researches, such as inertial confinement fusion (ICF), there are the harsh demands for the irradiation uniformity on the target surface with high-power laser. Achieving uniform irradiation of laser intensity on the target is a critical factor in experiments and also the forefront of current issues in the field, which has important academic value and practical significance. In this thesis, array uniform irradiation optical systems are studied, and the following main results are listed:1.An orthogonal cylindrical lens array (OCLA) optical system is presented for uniform irradiation on target surface.Based on the paraxial matrix optics and scalar diffraction integral theory, we put forward the designing principle of the OCLA system and the analytical expression of the intensity distribution; simultaneously, the OCLA system both in far field and in semi-far field has also been considered. Through numerical simulation, the smoothing characteristics and optimized designing for this system are obtained in details.The elimination of large-scale non-uniformity with the defocused irradiation and diffraction-weakened methods are proposed.2.Two kinds of point-focusing array systems with controllable focal spot are proposed:(a) lens arrays optical system with vari-focal-spot, and (b) orthogonal cylindrical lens arrays (OCLA) system with controllable focus length. Based on the paraxial matrix optics and generalized diffraction theory, the principles of the two vari-focus array optical systems, and the optimization of these optical systems parameters are analyzed in details. The smoothing performances of the two vari-focal array systems are confirmed by the numerical simulation and the theoretical calculation with Zemax optics design software.3. The variation in small-scale non-uniformity (SSINU) of intensity in crossed segmented wedge array (CSWA) focus system is studied theoretically and experimentally. Based on the physical optics, the separation between the major interference maxima and secondary maximum of interference fringes for the CSWA focus system are derived firstly. The variation of the SSINU has been confirmed by the numerical calculations on the basis of the Collins formula and ABCD propagation matrix theory.From the theory and experiment, we have studied the two methods of reducing the SSRNU, named after the deviation of wedge angles (DWA) and the off-focal laser radiation on target (OFLRT), and results demonstrated that they have a quite good agreement. The DWA, the OFLRT, and their optimized parameters are presented.4. Suppression of small-scale non-uniformity is realized, using the combination of the orthogonal cylindrical lens array and polarization control plate.The smoothing performance of the scheme is also analyzed by the detailed three-dimensional simulations with GLAD physical optics software. Moving the target slightly away from the exact focal plane of the principal focusing lens, a well-irradiating laser spot with small non-uniformity and great energy efficiency can be obtained accordingly.5.Based on propagation law of partially coherent light (PCL) and generalized diffraction theory, a PCL model is established, in which a quasi-monochromatic spatially partial coherent light is described by Gaussian Schell-Model (GSM) beams through the lens array system. Detailed three-dimensional numerical calculations show that the partial coherent light is advantageous in smoothening effects and reducing the small-scale non-uniformity over the complete coherent light. Moving the target slightly from the exact focal plane of the principal focus, and taking advantage of the effect of lateral thermal conduction smoothing, the high spatial-frequency intensity fluctuation can be further eliminated, which indicates the best possible irradiation uniformity and energy efficiency on the target.更多还原