【作者】 秦山；

【导师】 何赛灵；

【作者基本信息】 浙江大学 ， 光学工程， 2007， 博士

【摘要】 随着光纤通讯技术和光纤传感技术的发展，能够与光纤兼容的光纤器件得到了广泛而深入地研究，其中光纤激光器由于其成本低、结构简单、配置灵活和光纤兼容等方面的优点，以及在光纤通讯系统、光纤传感、光谱分析、微波信号产生等领域的潜在应用前景，吸引了广大研究者的兴趣。然而，由于目前用于光纤激光器的许多增益机制在功率转换效率、输出稳定性或者输出谱宽等方面都有各自不同的内在缺点，限制了它们的性能和应用。本文针对用于光纤激光器的两种不同增益介质——掺铒光纤和拉曼光纤，以掺铒光纤放大器为切入点，在深入研究了这两种光纤放大器的基础上，重点对以多波长为主的光纤激光器做了较为系统、深入的理论和实验研究。具体而言，从实验和理论两个方面系统地研究了掺铒光纤放大器；研究了多波长激光原理和多波长滤波器；研究了光纤拉曼多波长激光器；分析了它们各自的优缺点和存在的问题。在此基础上，提出了一种新型的、应用于多波长光纤激光器的掺铒光纤和光纤拉曼的混合增益机制。理论上预期，该机制能够使室温下掺铒光纤放大内在的增益竞争得到很好的抑制，因而可以获得稳定多波长运行，并且同时具有掺铒光纤的高功率转换效率、低激光器阈值的优点。最终通过实验实现了基于该增益机制的、室温下能够高稳定性、高信噪比、功率均衡运行的多波长光纤激光器。并在理论上进一步分析和模拟了该混合机制的实现机理，理论结论与实验结果一致。实验表明，该混合机制并不同于两种增益机制简单的组合。基于相同的原理，本文也实验研究了我们所提出的混合增益机制在主动锁模脉冲光纤激光器中的应用，实验结果说明该混合增益机制同样能够有效的抑制模式噪声。另外也介绍了与本文课题关系密切的一些实验研究和设备制作过程，如基于铋基掺铒光纤的宽带ASE(放大自发辐射)光源的制作。主要内容如下：首先在绪论中分别简要介绍了激光器、光纤激光器的历史和现状；重点介绍了多波长光纤激光器的发展历史和研究现状，特别对于掺铒光纤、拉曼光纤、半导体泵浦光源、谱滤波器等关键器件的研究现状作了综述；介绍了基于掺铒光纤放大、光纤拉曼散射、光纤布里渊散射和半导体光放大器等不同的增益机制的优点和缺点；最后讨论了多波长光纤激光器面临的问题。第二，系统地介绍了掺铒光纤放大器的基本理论；介绍和推导了掺铒光纤放大器的基本理论模型；介绍了掺铒光纤基本参数的测量测试方法；提出并实验研究了一种新型结构的低噪声、高增益掺铒光纤放大器；研究了铋基掺铒光纤的特性，实验研究了一种基于铋基掺铒光纤的宽带ASE光源。第三，对影响激光器多模振荡稳定的介质增益和损耗属性，如谱线展宽机制、增益饱和、模式竞争等概念，作了系统地分析；介绍了激光器多模振荡的速率方程；以Sagnac环形滤波器为代表，理论和实验分析了F-P谐振腔、谱滤波器等构成多波长光纤激光器的关键器件。第四，系统地从理论上介绍了光纤拉曼受激散射的增益机制，以及四波混频等非线性效应的影响，从半经典电磁理论出发，推导了它们的基本耦合方程，对一些重要的基本参数的测量方法和测试过程作了介绍，提出并实验研究了基于光子晶体光纤Sagnac环形滤波器的光纤拉曼多波长激光器。第五，该部分包括了本文的主要工作内容和主要创新点。实验比较了掺铒光纤和拉曼光纤增益特性的不同和对多波长激光器输出的影响；进而提出了基于掺铒光纤和光纤拉曼混合增益机制，进行了针对基于该混合增益机制的多波长光纤激光器实验研究，实验表明，该混合机制并不是两种放大器简单的组合，掺铒光纤在增益中起主导作用，而拉曼光纤对输出光功率的贡献要小很多；以已经获得的实验证据为基础，理论分析和模拟了该混合增益机制支持稳定多波长运行的机理，获得了与实验结果一致的结论；介绍了不同实验装置的设计和研究过程，并进一步提出了波长间隔可调、输出波长范围可控的的实验改进方法。第六、介绍了掺铒光纤和光纤拉曼混合增益机制在主动锁模光纤激光器的应用研究，实验证明该混合增益机制同样能够有效抑制掺铒光纤主动锁模激光器的超模噪声。最后，对本文的内容作了总结，分析了多波长光纤激光器的趋势，提出了展望，指出在拉曼增益特性等方面可能的研究方向。总之，本论文围绕多波长光纤激光器的研究热点问题，从理论和实验上研究了基于光纤拉曼和掺铒光纤混合增益机制、室温下稳定的多波长光纤激光器，我们相信这一成果能对科研生产起一定的指导作用。更多还原

【Abstract】 With the development of the fiber communication technology and fiber-optical sensor technology, the optical devices which are compatible with optical fibers have been studied widely and in depth. Because of their advantages such as low cost, high reliability, flexible configuration and compatibility with fibers, and the potential applications in e.g. fiber communication systems, fiber sensors, optical spectrum analysis and RF generation, fiber lasers have attracted great interests. However, the intrinsic shortcomings in various current fiber lasers including multi-wavelength fiber lasers (MWFLs) such as power conversion efficiency gains, output stability and output spectral width, have influenced the performance and limited their applications.In this dissertation, we started with the studying of two different gain mechanisms used in fiber lasers — fiber Raman amplification and Erbium-doped fiber (EDF) amplification. By comparing the advantages and disadvantages between them, we focused the attention on MWFLs and proposed a novel hybrid gain mechanism which was used in MWFLs to suppress the intrinsic gain competition in Erbium-doped fiber amplifiers (EDFAs). Finally, a set of stable and uniform MWFLs in room temperature were obtained in our experiments.The theoretical analysis and numerical simulation on this hybrid gain mechanism were also proposed and the results showed that it can support stable operation of the fiber lasers.Another experiment was shown that this hybrid gain mechanism can also be applied in active mode-locked EDF lasers (AML-EDFLs) to suppress the supermode noise due to the gain competition in EDFA.This dissertation is organized as follows:In the introduction chapter, the history and present status of lasers and fiber lasers were introduced, and more attention was focused on the development process and current situation of MWFLs. In particular, the status of some key devices such as erbium-doped fibers, Raman fibers, pump sources and spectral filters were reviewed. The advantages and disadvantages of EDFAs, fiber Raman amplifiers (FRAs) and Semiconductor optical amplifiers (SOAs) were also introduced. At the end of this chapter, the main problems faced by MWFLs were presented.In chapter 2, the basic theory of EDFAs was studied, and the basic theoretical model was introduced and derived. Then, methods and processes of test and measurement on some important basic parameters of EDF were introduced. And then, an L-band EDFA with low noise and high gain was proposed and studied. Additionally, an ultra-broadband amplified spontaneous emission (ASE) source based on Bi-EDF was also studied and demonstrated.In chapter 3, characteristics of the medium gains and losses that impact the stability of multi-mode laser resonator, such as line broadening, gain saturation and mode competition were analyzed systemically. The rate equation of a multi-mode resonator was also studied.Then, taken the Sagnac loop filter as a main example, some key devices such as the resonators and spectral filters were analyzed theoretically and experimentally.In chapter 4, the stimulated Raman scattering (SRS) in fiber including some other nonlinear effects such as four-wave mixing (FWM) was studied theoretically. Then, the basic rate equations and coupled equations were derived from the semi-classical electromagnetic theory. And then, methods and processes of test and measurement on some important basic parameters for FRA were introduced. Finally, a Sagnac loop filter employed a section of photonic crystal fiber (PCF) was presented and a Raman MWFL was demonstrated in experiments.In chapter 5, the main tasks and major innovations of this dissertation were contained in this part. The different characteristics between EDF and fiber Raman gains were first compared experimentally, and then the hybrid gain mechanism based on EDFA and FRA was proposed. Furthermore, several MWFLs with various structures utilizing this hybrid gain mechanism were designed and studied. Since the gain of EDFA was much greater than the one of FRA, the hybrid gain mechanism can not be regarded as a simple combination of FRA and EDFA. With the experimental evidence on the absence of cross-saturation effects in fiber Raman, theoretical analysis and numerical simulation on the operation principle of this hybrid gain were proposed and the experimental results can be explained very well. Then, two novel methods of channel-spacing tunable and output wavelength range controllable MWFLs utilizing were proposed respectively.In chapter 6, the hybrid gain was used in AML-EDFLs, and the experimental results also show it can suppress the supermode noise in AML-EDFLs.In summary, this dissertation focused on the hot point of MWFLs, a novel method to obtain stable and uniform MWFLs in room temperature was proposed, and several important problems of MWFLs were studied theoretically and experimentally. Both theoretical and experimental results can play a role in guiding study on MWFLs.更多还原