随机表面对连续与超快相干光波的散射及其随机光场研究
文献类型：学位论文
| 作者 | 程传福 |
| 学位类别 | 博士 |
| 答辩日期 | 2004 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 徐至展 |
| 关键词 | 随机表面 散射 散斑 近场光学 超快激光 |
| 其他题名 | The light scattering of random surfaces under continuous and ultrafast coherent illuminations and its random light fields |
| 中文摘要 | 随机表面及其散射，标识研究是现代光科学与技术的重要前沿领域，而且对与随机表面有关的其他许多科学技术的前沿领域如薄膜生长动力学、天体冲击引起的断裂、微电子元器件设计等也具有重要的学术意义和广泛应用前景。光波作为波长量级的探针，通过振幅和相位的分布及变化携带物理过程的信息。近年来近场光学和超快激光的发展，使光波探针在空间和时间上达到超高和超快分辨，为人们认识物质世界提供了全新的手段。研究连续和超快相干光波经随机表面散射后从近场到远场范围内的传播规律，是建立和应用该手段的重要基础。本学位论文结合了随机表面的散射、近场及超快光学等物理学前沿领域最新成果的理论与方法，对随机表面在连续与超快相干光波照明下的散射、随机光场特性和表面的标识等进行了一系列创造性的研究工作。在理论上，提出和解决了随机表面散射和随机散斑光场中的新概念和重要问题，如散射光强轮廓半宽度的数学解析、近场散斑概念和超快光谱散斑概念的提出等；在数值模拟计算中，解决了光散射模拟和随机光场数值计算中的一系列关键问题，如提出了自仿射分形随机表面的产生算法、建立了联结象面光强与表面结构函数的补偿算法、在时域上拓展了用于超快过程的格林积分方程数值求解算法等；在实验上，建立了随机表面光学标识的新方法，如角分辨的光散射及相位恢复法测量随机表面的高度概率分布、变孔径象面散斑光强提取表面相关函数、无预标的象面散斑对比度法测量随机表面参数等。概括起来，本学位论文取得了以下主要创新成果：1．首次提出了表面高度概率分布标识的角分辨光散射理论与实验方法，探索并成功运用了光学逆问题的迭代算法（Gerchberg-Saxton算法）恢复光散射镜面反射分量光强以波矢量为函数的相位分布。通过镜面分量光强随入射角度变化的实验测量，并根据理论结果实现了随机表面高度概率的信息提取。这是逆光学算法应用领域的开拓和表面标识研究的创新。2．把随机表面散射的光场特性研究拓展到近场光学领域，首次提出了近场散斑的概念。通过介质分界面上光场积分方程求解的数值算法实现，以及对自仿射分形表面散射的近场光强的计算，发现了近场散斑的存在并研究了其传播规律，如散斑存在分形结构并在经过一个波长的传播消失、对比度在近场区域附近达到饱和等；在原理上对近场散斑的形成机理进行了探索。这为近场散斑这一新方向的研究奠定了基础。3．建立了由散斑光强获取随机表面高度相关函数的理论和数值补偿算法，并首次在实验上实现了用散斑方法对高度相关函数的提取。采用了变孔径的成像系统进行散斑光强测量，创造性地提出了采用数值方法来弥补像面散斑强度测量数据与表面结构函数的数学关系之间的缺陷，将光强与孔径的数值关系转化为相关函数的傅立叶变换对，进而恢复出表面的高度相关函数。4．率先将随机光场研究拓展到超快激光领域，引入了超快远场散斑和超快光谱散斑的概念。在理论上研究了超快激光照明的条件下，菲涅耳衍射区超快散斑场的形成及变化的全新规律，如散斑颗粒中存在干涉条纹结构及其空间周期随时间减小等，在实验上观察了超快光谱散斑，证实了超快散斑的存在。5．将近场光学与超快光学结合起来，研究了超快近场散斑的规律。在时域上拓展了电磁场计算的求解格林积分法数值算法，研究了超快光脉冲经亚波长小孔的近场衍射后在介质分界面上光强的节点、脉冲的展宽与分裂等；发现了超快近场散斑的颗粒随时间减小、对比度不断增加等特有规律。这对于超快光波在界面上建立与传播研究的开展具有重要意义，也将成为正蓬勃发展的前沿学科超快物理学的重要内容。此外，本学位论文还在光散射轮廓的半宽度、自仿射分形随机表面后面附近散斑自相关函数的分析及由其提取表面信息、无预定标测量随机表面粗糙度和横向相关长度的散斑对比度法等也开展了有创新的研究。本文的研究I作被《Applied Phsics Letters》、《optics Letters》、《PhysicalReviewE》、《Europhysics Letters》和《APplied optics》等国际著名的物理学和光学期刊连续快速发表，并得到国际同行的关注和高度评价。例如，《AppliedPhysics Letters》的审稿人对角分辨的光散射法提取高度概率的研究成果给予了高度评价，指出这一“提出了巧妙方法”，t‘解决了重要问题，具有足够的新意（new）、原始性（original）和创新胜（innovative）”。再如，《 optics Letters》的审稿人对近场散斑研究的评价中指出“是新的重要研究领域，因此我推荐迅速在《onticsLetters》发表”。 |
| 英文摘要 | The studies of random surfaces and their light scattering under continuous and ultrafast coherent illuminations are the frontier areas in modern optical science and technology. With great academic significance and application potentials, they also have great influences on many other frontier fields such as film growth dynamics, dynamic fracture by large extraterrestrial impacts and electronic micro-devices. As a probe of the order of wavelength, light wave takes along the information of a physical process in its amplitude and phase distributions. With the rapid development of near-field optics and ultrafast laser in recent years, the light wave probe has reached an ultra-high spatial and ultrafast temporal resolution, which provides novel means for people to understand the physical world. The studies of the propagations of the continuous and ultrafast coherent light waves scattered from random surfaces in the near- and far-field regions are the foundations for the construction and application of this means. Combining methodologies and the theories in the achievements in such frontier areas of physics as scattering of random surfaces, near-field optics and ultrafast optics, this dissertation conducts a series of creative researches in the characterization of random surfaces, scattering of random surfaces and the properties of random light fields under the illuminations of continuous and ultrafast lasers. In the theoretical studies, we propose the new concepts and deal with the important problems in light scattering and in random speckle light fields, such as mathematical analysis of the half-width of the scattered intensity profiles and the proposition of the concepts of near-field speckles and ultrafast spectrum speckles. In the numerical simulations, we have tackled a series of key problems in the calculations of light scattering intensities and random light fields, such as proposing the algorithm for the generation of the random self-affine fractal surfaces and the complimentary algorithm of connecting the image intensity and the surface structure function. In experimental studies, we validate several novel methods for random surface characterizations and for the measurement of random light fields, examples of which are angle resolved light scattering with phase retrievals for the measurement of the height probability density of random surfaces, the extraction of height correlation function from the image intensity by using a variable aperture optical system, and the non-precalibration measurement of random surface parameters. The major achievements are summarized as following: 1. We propose for the first time the theory and the experimental method of the angle resolved light scattering for the height probability density measurement, and make successful use of the iterative optical inversion algorithm (Gerchberg-Saxton algorithm) to reconstruct the phase distribution of specular component of scattered intensity as a function wave vector. Based on the theoretical results, the height probability density is extracted from the experimental data, of the specular intensity versus the angles of incidence. This is both the extension of the applications of the optical inversion algorithm and the advance in the surface characterizations. 2. We extend the studies of random light fields produced by rough surfaces to the area of near-field optics, and propose the concept of near-field speckles. By numerical solutions of the integral equations of light waves at the medium boundaries, and then by the calculations of the light intensities produced by random self-affine surfaces in the near-field region, the existence of speckles in this region is verified and the their properties are studied. It is found that the speckles have fractal characteristics that disappear after the propagation of one wavelength. The speckle contrast saturates in the near-field. The mechanism of the formation of near-field speckles is analyzed. This work lays the foundation for opening up the new subject of near-field speckles. 3. The theory and the complementary algorithm are constructed to acquire the correlation function of the random surface height, which is realized for the first time experimentally. By measuring the average intensities of the speckles in an optical imaging system with the variable aperture, we propose the numerical method to complement the deficiency in the mathematical relation between the speckle intensity and the surface structure. The intensity data versus the aperture diameter are then converted to the Fourier-transform pair, and then the correlation function of the surface is retrieved. 4. The studies of the scattering from random surfaces and the random light field are extended for the first time to the area of ultrafast optics, and the concepts of ultrafast speckles and ultrafast spectrum speckles are introduced. Theories are developed for explanation of the formation and the never-before understood behaviors of the speckles in the Fresnel diffraction region under ultrafast laser illuminations. Such behaviors include the structures of the interference fringes in the speckle grains and the decrease of the spatial period, etc. The existence of the ultrafast speckles is verified by the experimental observation of the untrafat spectrum speckles. 5. Combining near-field optics and ultrafast optics, we study the properties of ultrafast near-field speckles. We revise the algorithm of the numerical solutions of the integral equation for electromagnetic waves in the time domain. In the studies of the diffraction of ultrafast laser pulse by a subwavelength aperture, the fundamental laws of the ultrafast near-field wave are exposed such as the formation of nodal points in intensities and the spread and the splitting of the pulse. The unique behaviors of the ultrafast near-field speckles are also found such as the decrease of the speckle grain size at the medium interface and the increase of the speckle contrast with time elapsing. The study is of importance for pioneering the new areas of speckles and light propagations, and will be one of the important parts of the ultrafast physics, a vibrantly developing frontier science field. In addition, we have also made achievements in other subjects as the half-width of the profile of scattered light intensity, autocorrelation function of speckles near the random self-affine fractal surfaces and the extraction of surface parameters, the speckle contrast method for the non-precalibration measurement of surface roughness and lateral correlation length, ect. The researches of this dissertation have been continually and rapidly published in the worldwide famous physics and optics journals, such as Applied Physics Letters, Optics Letters, Physical Review E and 'Europhysics Letters, and have attracted the attentions and the highly favorable comments of the international experts. For example, the reviewer of Applied Physics Letters has giving the following comment on our work of the extraction of height probability density. '"This is a clever method", and "there is enough that is new, original and innovative in this paper, which deals with an important problem". In the comment on the work of near-field speckles, the reviewer of Optics Letters has pointed out that "this area of study is novel and important, and I hence recommend rapid pulication in Optics Letters". |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15571]  |
| 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 | 程传福. 随机表面对连续与超快相干光波的散射及其随机光场研究[D]. 中国科学院上海光学精密机械研究所. 2004. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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