【作者】 任晓荣；

【导师】 程传福； 徐至展；

【作者基本信息】 山东师范大学 ， 光学， 2004， 硕士

【摘要】 近场光学是研究距离物体表面一个波长以内(即近场区域)的光学现象的新型交叉学科。随着近场光学显微镜的快速发展，对近场光学的研究无论在理论上还是在实验上都获得了相当大的进展，但对近场散斑特性的研究还处于探索阶段。本文用数值格林函数法对随机表面的近场散斑和超快近场散斑的特性进行了计算模拟和理论研究。全文共分四章。 第一章对随机表面的描述、光散射的基本原理、随机光场的特性、近场光学和近场散斑以及超快近场散斑的特性进行了综述。 第二章提出了由格林函数法和边界条件来计算模拟随机表面产生的近场随机光场的方法，并将这一方法与基尔霍夫近似法进行比较。模拟计算了长度不同且具有不同表面参量的自仿射分形表面样本所产生的近场散斑场，得出近场散斑的许多特性，并模拟了离开表面不同距离处的近场散斑场的传播过程。格林函数法与基尔霍夫近似法相比，在随机表面粗糙度比较小时，基尔霍夫近似的精度比较高。在粗糙度相同的情况下，表面的分形维数越小，基尔霍夫近似的精度越高。 第三章应用格林函数法计算模拟了飞秒激光脉冲通过自仿射随机表面后在近场产生的光场。我们计算并研究了不同时间宽度的飞秒激光脉冲通过不同参数的表面的近场散斑特性，我们发现飞秒激光脉冲的近场散斑与入射激光脉冲和表面都有着密切的关系。 第四章将格林函数法应用于计算超快激光脉冲的小孔衍射。我们分析了飞秒脉冲沿界面的传播过程，并且发现在该传播过程中，光波在介质的分界面上和在接近界面的区域中形成光强的节点，光波脉冲的时间宽度会发生展宽，并且在节点附近的空间点处的光强脉冲会产生时间的分裂，分裂成两个脉冲。更多还原

【Abstract】 Near-field optics is a new interdisciplinary subject which studies the optical phenomena within one wavelength, and it breaks free from the limitation of conventional optical resolution. With the rapid development of near-field optical microscopy in recent years, considerable advancement has been achieved theoretically and experimentally in the studies of near-field optics. This paper is concentrated on simulational and theoretical studies on the the properties of near-field speckles of the random surfaces and the femtosecond laser pulses. The whole paper is divided into four chapters.In chapter 1, we gives a summary and review of the description of random surfaces and its near-field speckles, the fundamental theories of light scattering, the properties of random light fields and near-field optics.In chapter 2, we present a method with Green functions and the boundary conditions for the simulational generation of light scattering from random surface with arbitrary parameters, and compare this method with the method of Kirchhoff approximation and near-field light scattering and speckle field. We simulate near-field speckles generated by the self-affine fractal surface samples with different surface parameters and different length, and then study in detail them and discover some properties of the near-field speckles. We also simulate the transmission of light scattering with different distance from the surface. When we compare the method of the Green’s function with the method of Kirchhoff approximation, we find that the smaller the roughness of random surfaces is, the higher theprecision of the Kirchhoff approximation is. At the condition of the same roughness, smaller the roughness exponent of random surfaces is, the higher the precision of the Kirchhoff approximation is.In chapter 3, by use of a numerical calculation based on Green’s integral equation, we study the near-field speckles produced by the random self-affine fractal surfaces of a dielectric medium. We computer and study the properties of the near-field speckles produced by random self-affine fractal surfaces with different surface parameter illuminated by the femtosecond laser pulses with the different temporal width, and find that the near-field speckles have a close relationship with the femtosecond laser pulses and the random self-affine fractal surfaces.In chapter 4, we calculate and study the diffraction of the femtosecond laser pulse propagating through a subwavelength aperture with the method of the Green functions. After the femtosecond laser pulse propagate through a subwavelength aperture they propagate along the interface, and in the propagating process the light wave, the nodes of the light intensity are produced at the interface and the region near the interface, the temporal width of the femtosecond laser pulses will be broadened, and the light intensity at the spatial points near the nodes will be splited into two pulses with respect to time.更多还原