多模光纤中基于受激布里渊散射的光束净化效应研究

发布时间：2018-01-07 07:16

本文关键词：多模光纤中基于受激布里渊散射的光束净化效应研究　出处：《哈尔滨工业大学》2016年博士论文　论文类型：学位论文

【摘要】：受激布里渊散射(Stimulated Brillouin Scattering,SBS)在光纤领域的研究中一直处于十分重要的地位。一方面,人们渴望抑制光纤中的SBS效应所带来的各种不良影响;另一方面,科学家们又利用SBS特性进行了有关光纤传感、慢光和相位共轭等有利因素的研究并广泛应用于通信、建筑等诸多领域。此外,多模光纤的SBS研究中还发现过一种称之为SBS光束净化的特殊效应,它能将光束质量恶劣的多模光束转化成为良好光束质量的基模光束。SBS光束净化效应的发现为多模光纤中光束质量的改善提供了一条有利途径,但这种效应却违背了人们对于SBS具有相位共轭特性的传统认识。自1993年SBS光束净化效应被发现以来,国际上不少课题组都开展过相关研究,但至今仍没有一套比较完整、合理的理论来解释SBS光束净化,甚至关于SBS光束净化的发生条件及产生原因都还各执一词。本论文便针对多模光纤中的SBS光束净化进行了系统的理论和实验研究,建立了一套较为完整的SBS光束净化理论模型,合理解释了SBS光束净化的产生机制并明确提出了SBS光束净化的发生条件,还实验改善了之前泵浦转化效率低下、输出光束不稳定等制约其应用的关键性问题。首先,我们建立了适宜于分析多模光纤中模间SBS过程的三维SBS耦合波方程。该方程解决了传统平面波近似的SBS耦合模型下因忽略模式横向分布而无法分析不同模式间SBS差异的问题,同时使用弹性动力学理论建立声子场方程,更正了传统耦合波方程中的流体参数。根据三维SBS耦合波方程的形式解,我们指出了多模光纤与体介质中SBS过程的区别并提出了使用布里渊模间增益系数‖来分析不同模式间布里渊增益差别的方法。其次,我们通过对三维SBS耦合波方程进行仿真分析给出了轴对称型多模光纤中各模式间布里渊增益的分布曲线,理论预测了各种光纤参数对模间布里渊增益的影响。根据理论结果,我们明确提出了多模光纤中发生SBS相位共轭和光束净化的物理机制和产生条件,揭示了SBS光束净化的本质并加以实验佐证。最后,我们还根据理论指导利用大芯径的折射率渐变光纤实验实现了高质量、高泵浦转化效率的SBS光束净化,改善了限制SBS光束净化应用的关键技术,同时还研究了SBS光束净化中影响泵浦转化效率及输出光束质量的理论和实际因素,讨论了SBS光束净化的应用前景。
[Abstract]:Stimulated Brillouin scattering (SBS) has been playing an important role in the field of optical fiber. People are eager to suppress all kinds of adverse effects caused by SBS effect in optical fiber. On the other hand, scientists have made use of the characteristics of SBS to study the advantages of optical fiber sensing, slow light and phase conjugation, and have been widely used in many fields, such as communication, architecture and so on. A special effect called SBS beam purification has also been found in the SBS study of multimode optical fiber. It can transform the bad multimode beam into a good beam quality. The discovery of the purifying effect of SBS beam provides a good way to improve the beam quality in multimode fiber. However, this effect is contrary to the traditional understanding that SBS has phase conjugation characteristics. Since the SBS beam purification effect was discovered in 1993, many international research groups have carried out related research. However, there is still no complete and reasonable theory to explain the SBS beam purification. Even about the conditions and causes of SBS beam purification, this paper makes a systematic theoretical and experimental study on SBS beam purification in multi-mode optical fiber. A complete theoretical model of SBS beam purification is established. The mechanism of SBS beam purification is explained reasonably and the conditions of SBS beam purification are put forward. The experiment also improves the key problems which restrict its application, such as the low efficiency of pump conversion and the instability of the output beam. We have established a three-dimensional SBS coupling wave equation suitable for analyzing the SBS process between modes in multimode optical fiber. This equation solves the problem that the traditional plane wave approximation SBS coupling model can not be analyzed because of neglecting the transverse distribution of the mode. The problem of SBS differences between different patterns. At the same time, the phonon field equation is established by using the theory of elastic dynamics, and the fluid parameters in the traditional coupled wave equation are corrected. According to the formal solution of the three-dimensional SBS coupled wave equation, the solution is obtained. We point out the difference of SBS process between multimode fiber and bulk medium and propose a method to analyze the difference of Brillouin gain between different modes by using the gain coefficient between Brillouin modes. The distribution curve of Brillouin gain in axisymmetric multimode fiber is obtained by simulating the three-dimensional SBS coupling wave equation. The influence of various optical fiber parameters on Brillouin gain is predicted theoretically. Based on the theoretical results, the physical mechanism and generation conditions of SBS phase conjugation and beam purification in multimode optical fiber are proposed. The essence of SBS beam purification is revealed and verified by experiments. Finally, we use the refractive index gradient optical fiber with large core diameter to achieve high quality. The SBS beam purification with high pump conversion efficiency improves the key technologies that limit the application of SBS beam purification. At the same time, the theoretical and practical factors affecting pump conversion efficiency and output beam quality in SBS beam purification are studied, and the application prospect of SBS beam purification is discussed.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN253

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