【作者】 黎明；

【导师】 林殿阳；

【作者基本信息】 哈尔滨工业大学 ， 物理电子学， 2007， 硕士

【摘要】 光与物质的相互作用无论在科学上还是技术上都具有非常重要的意义。聚合物作为一类新型非线性光学的材料受到广泛的关注和研究,它们在光存储、微光学、纳米技术等领域具有广泛的应用前景。本论文从实验上研究了均匀聚异戊二烯溶液中的光斑变化现象,利用光诱导折射率变化理论分析了光斑变化的规律,并对光诱导折射率变化的机理进行了探讨。在理论上利用光诱导折射率变化理论,分析了高斯光束通过样品后,样品的不同折射率特性对透射光斑的影响,获得了透射光斑随聚焦透镜位置、样品长度、入射光波长等的变化规律。在实验上用聚焦的连续激光照射均匀聚异戊二烯溶液时观察到入射的高斯光斑逐渐扩展成具有同心环状结构的光斑,并最终变成了散射斑。光斑的结构、光环数量和变化速度与入射光强和溶液浓度及聚焦透镜位置有关:入射光越强或溶液浓度越高时光斑变化快,衍射环多;入射光越弱或溶液浓度越低时光斑变化慢,衍射环少;入射光为发散光时形成的光斑中心亮;入射光为会聚光形成的光斑中心暗;这种现象还具有记忆功能,记忆时间可以达到数天以上;溶剂中加入C60后,溶质的溶解速度加快,吸收增加,光学均匀性变好,诱导光斑变化所需的激光功率降低,光斑变化过程加快。不同波长(波长为632.8nm和532nm)的激光照射,产生的现象基本相同,只是光斑变化的速度稍有不同;单独对溶剂进行照射没有产生变化;入射光非聚焦的状态下也没有观察到这种现象。通过对实验结果的分析和讨论,发现这种现象与光克尔效应导致的折射率变化规律类似,但排除了这种现象由光克尔效应和光热效应引起的可能性。为了解释光诱导折射率变化产生的原因,我们提出了一个由聚异戊二烯溶液产生光交联聚合导致折射率变化的假设,并对实验现象作出了初步解释。更多还原

【Abstract】 The interactions of laser with matter have extreme scientific and technological importance. Polymers, as a kind of new material for nonlinear optics, have been paid wide attention and studied. They could have potential applications in the fields of photorefractive, microoptics, nanotechnology, and so. In this dissertation, the pattern formations in homogeneous polyisoprene solutions, induced by a CW laser are studied experimentally, the dependence of the light pattern on the refractive index change induced by a laser are analyzed theoretically, and the mechanism of the refractive index change in homogeneous polyisoprene solutions induced by a laser are explored.Using the theory of the refractive index change induced by a Gaussian laser, the effects of the light pattern on the different are analyzed, and the dependence of the light pattern on the position of focal lenses, sample length and laser wave length are obtained. In the experiment, a CW laser is focused into the polyisoprene solution, the changes of the light patterns are observed. The incident Gaussian beam is expanded into a diffraction-ringed beam and eventually changes into speckle. The pattern, number of the diffraction rings and changed speed of the pattern have relation with the incident light intensity, solution concentration and position of the lens focus: the stronger the incident laser or the bigger the solution concentration, the faster the pattern changed, and the more the number of the diffraction rings observed; the weaker the incident laser or the smaller the solution concentration, the slower the pattern changed, and the less the number of the diffraction rings observed. The different positions of the lens focus produce different diffraction rings. When the focus is located in front of the sample or in the sample, the center of the spot is bright. When the focus is behind the sample, the center of the spot is dark. The experiment shows that once the pattern is formed, its effect can be maintained for many days. When C60 is added into the solvent, the laser power of induced pattern formation is reduced, and the process of the pattern changed become faster. When the incident laser wavelength (632.8nm and 532nm) is different, the experimental phenomena observed are basically same, but the changing speeds are slight different. When an unfocused laser beam is used, the pattern formation is absent.Analyzing and discussing the experimental results, it is found that the pattern change is like the refractive index change caused by the optical Kerr effect. But the possibility of the refractive index caused by the optical Kerr and thermal blooming effects are excluded. In order to explain the mechanism of the refractive index change in polyisoprene solutions induced by a laser, a proposition, the cross linkage polymerization produced by polyisoprene solution causes the change of refractive index, is given, and the experiment results are explained.更多还原