光折变晶体中若干实验现象研究-物理电子学专业论文.docxVIP

I I 摘 要 光折变晶体在光学图象处理、光学数据存储、光互连、光计算以及在未来的光信 息技术中都有着广泛的应用前景。有关光折变材料的应用研究一直以来备受人们关注。 而这些光折变的应用一定程度上是以光波在光折变材料中的耦合和光折变空间光孤子 为基础的，因此进行光折变晶体中的双光束耦合和空间光孤子实验探讨十分必要，本 文正是基于此目的在光折变晶体中展开相关实验研究。 论文首先从 Kukhtarev 带输运模型出发，从理论上分析了光折变材料中的空间电 荷场的建立及其调制折射率的过程。重点讨论了双光束耦合作用，从理论上分析了双 光束耦合中的能量及相位耦合过程。然后介绍了光折变空间孤子的相关理论，具体介 绍了自相位调制自聚焦机制形成的空间孤子及非线性相位耦合机制形成的空间孤子理 论模型。通常又把通过非线性相位耦合机制形成的空间孤子称为全息孤子。本文介绍 的全息孤子是基于双光束耦合作用形成的空间孤子，依据是否考虑损耗的影响，全息 孤子又分为哈密顿全息孤子及耗散全息孤子。 本文依据光折变相关理论，在铁电晶体 LiNbO3 中的进行双光束耦合实验，讨论了 外加电场对光折变晶体中双光束耦合的相移影响。在光伏晶体 Cu:KNSBN 中进行空间光 孤子的实验，成功观测到光伏明孤子和耗散全息孤子，并对影响光伏明孤子的背景光 强度及影响耗散全息孤子的泵浦光与信号光的夹角分别进行了实验探讨。 关键词：光折变效应 空间光孤子 双光束耦合 耗散全息空间光孤子 铌酸锂晶体 钾钠铌酸锶钡 II II Abstract Photorefractive crystals have many potential applications in optical image processing, optical data storage, optical interconnection, optical computers, and in future optical information technology. The application study on photorefractive materials has attracted more and more people’s attention. Such applications are somewhere based on two-beam coupling and spatial optical solitons in photorefractive crystals. So it is very necessary for the experimental exploratory development of photorefractive effects in this field. For this purpose, we develop the correlation experimental study on some problems of photorefractive effects in this thesis. The forming mechanism of space-charge field and its influence on the refractive index of nonlinear materials are derived based on the Kukhtarev model. And the interaction of two laser beams inside a photorefractive medium is discussed, the intensity and phase coupling processes are analyzed. Then, relevant theories of photorefractive spatial solitons are presented. Spatial solitons generally can be classified into two generic types: The first type is originated from the self-phase modulation self-focusing mechanism, and the second type is originated from the mechanism that arises from the nonlinear phase coupling. Normally, we call the spatial solitons arises from the nonlinear phase coup