掺铒光纤环形激光器频域动力学特性及演化规律研究

发布时间：2018-05-24 14:15

本文选题：光纤激光器 + 频域动力学　；参考：《国防科学技术大学》2015年博士论文

【摘要】：论文针对光纤环形激光器(FRL)在工程应用中出现的复杂多模动态现象,通过改进多通道实时频域观测手段,突破传统激光动力学测量技术的频域限制,将人们对FRL非线性动力学特性的认识从低维拓展至高维,揭示了模式个体行为与集群行为之间的复杂关联及内在物理机制。激光频域动力学问题是光学复杂系统研究领域的一大难题。FRL是典型的大自由度光学复杂系统,具有复杂跳模、高维混沌等非线性模式动态行为。现有的理论模型及测量手段大多只关注密集模式群落的整体行为,而忽视了模式个体行为;这一降维处理方式丢失了大量的频域模式动态信息,导致跳模抑制、高维频域混沌产生及控制等频域非线性动力学问题无法得到有效处理。要解决这些问题,需在理论上建立包含密集纵模间相互作用与耦合机制的物理模型,更需发展多模激光模式动态行为测量的实验手段。论文以掺铒光纤环形激光器(EDFRL)作为研究对象,通过引入密集纵模间的交叉耦合系数,并考虑铒离子对猝灭效应而引入额外自由度,建立了双模及多模光纤激光频域动力学模型,可有效描述频域内大量模式的个体行为及集群行为,在理论上重现了频域高维动力系统所特有的多模动态特性。仿真结果表明,通过改变离子对浓度或抽运系数,所有模式可通过阵发、倍周期分岔、准周期等途径同步进入混沌,关联维数高达5.1。为实验获取光纤激光多模动态信息,提出一种基于光学外差和时频分析技术(OH-JTFA)的频域动态测量方法,实现了EDFRL密集模式频率及强度多参量时间序列的同步提取,频率分辨率在kHz量级。分别考察了单FBG选模EDFRL、自组织反馈EDFRL、调制型混沌EDFRL等三类光纤激光系统的频域动态特性,以揭示模式个体行为与群体行为间的复杂互动及演化规律。单FBG选模EDFRL常被认为是最典型的单波长激光系统,实际上在选模通道内寄居上百个本征模式,自由运转条件下输出非稳态多纵模(MLM)。通过采用OH-JTFA方法,首次清晰测得该类EDFRL输出密集多模呈现的丰富局域动态现象,发现模式群落整体行为处于光强稳态时,模式个体行为可呈现典型的混沌特征。自组织反馈EDFRL在腔内引入饱和吸收体形成超窄带自适应光栅,理论上可始终保持单纵模(SLM)稳定输出。然而,真实激光器存在多类型的跳模现象,受限于常规跳模检测手段,而无法有效获取跳模全过程的关键信息。通过采用OH-JTFA方法,实现了对跳模全动态过程的实时监测,跳模过程由时频瀑布图直观呈现,首次无失真地获取到跳模瞬态过程的所有物理参量。调制型混沌EDFRL通过引入一个自由度,使总光强呈混沌输出,是典型的低维混沌系统。同样,该系统输出光场包含大量密集纵模,当总光强输出为混沌态时频域内各模式动态特性及演化规律迄今仍不清楚。通过提高OH-JTFA的频域分辨率,同步提取出单个模式频率、谱线及光强等多参量时间演化特性;发现当总光强为低维混沌输出时,单个模式在频域上出现频率调制及谱线加宽现象、在强度上呈现高维混沌或随机特征。论文中得到的重要实验结果及创新点主要包括以下三个方面:1、通过OH-JTFA方法在单FBG MLM-EDFRL中发现了一类大自由度非线性动力系统所特有的动态现象。测量结果表明,局域模式产生了总光强所无法呈现的频域动态行为,包括模式自脉冲、模式反相动态、混沌多模振荡、随机多模振荡等。2、利用OH-JTFA方法首次获得了自组织反馈SLM-EDFRL典型跳模及瞬时多模振荡演化过程的时频瀑布图。本方法是迄今唯一能实现同步提取EDFRL跳模持续时间、跳模间距与方向、参与竞争的模式数量、模式强度演化等跳模参数的频域测量手段,为深入理解模式失稳及动态机理提供了更全面的观测手段,具有重要的参考价值。3、通过提高OH-JTFA的频域分辨率,考察了抽运调制型混沌光纤激光系统的频域动力学特性,发现了总光强表现为典型的低维混沌时,频域内存在的大量纵模表现出极为复杂的高维动态特性。对各模式进行的非线性时间序列分析表明具有混沌特性的模式与具有随机演化特性的模式在总的低维混沌下共存。在此基础上,进一步探讨了利用混沌光纤激光器频域内的大量混沌/随机模式作为光子熵源来生成多通道物理随机码的可行性。
[Abstract]:In this paper, the complex multimode dynamic phenomenon of fiber ring laser (FRL) is used in the engineering application. By improving the multi-channel real-time frequency domain observation method, the frequency domain limitation of the traditional laser dynamic measurement technology is broken through. The understanding of the nonlinear dynamic characteristics of the FRL is extended from low dimension to high dimension, and the individual behavior and set of the model is revealed. The complex association and internal physical mechanism between group behavior. The problem of laser frequency domain dynamics is a major problem in the field of optical complex systems..FRL is a typical large degree of freedom optical complex system with complex dynamic behavior such as complex mode jumping, high dimensional chaos and so on. Most of the existing theoretical models and measurement means are mostly focused on the intensive mode. The whole behavior of the community is ignored, and the pattern individual behavior is ignored. This way of reducing the dimensional dynamic information in frequency domain, which leads to the suppression of die hopping, and the nonlinear dynamic problems in frequency domain, such as high dimensional frequency domain chaos generation and control, can not be effectively dealt with. The physical model of interaction and coupling mechanism needs to develop the experimental means of dynamic behavior measurement in multimode laser mode. The paper uses an erbium doped fiber ring laser (EDFRL) as the research object. By introducing the cross coupling coefficient between the dense longitudinal modes and introducing the additional degree of freedom for the quenching effect of Erbium ion, the two mode and multi modes are established. The frequency domain dynamic model of the optical fiber laser can effectively describe the individual behavior and cluster behavior of a large number of modes in the frequency domain. In theory, the multimode dynamic characteristics peculiar to the high dimensional power system in the frequency domain are reproduced. The simulation results show that by changing the ion pair concentration or pumping coefficient, all patterns can pass through the formation, the period doubling bifurcation, the quasi periodic and so on. The path synchronization enters chaos, and the correlation dimension is up to 5.1. to obtain the multi mode dynamic information of optical fiber laser. A frequency domain dynamic measurement method based on optical heterodyne and time-frequency analysis technology (OH-JTFA) is proposed. The synchronous extraction of multi parameter time series of frequency and intensity in EDFRL intensive mode is realized. The frequency resolution is in the order of kHz. Single FBG mode selection EDFRL, self organizing feedback EDFRL, modulated chaotic EDFRL and other three kinds of optical fiber laser systems are dynamic in frequency domain to reveal the complex interaction and evolution law between mode individual behavior and group behavior. The single FBG mode selection EDFRL is often considered as the most typical single wavelength laser system, and in fact resides hundreds of eigenvalues in the mode selection channel. In the mode, the unsteady multi longitudinal mode (MLM) is output under free running condition. By using the OH-JTFA method, the rich local dynamic phenomenon of the EDFRL output dense multimode is clearly detected for the first time. It is found that the pattern community's behavior can show the typical chaotic characteristics when the whole behavior of the pattern community is in the light steady state. The self organizing feedback EDFRL is introduced in the cavity. The saturated absorber forms a super narrow band adaptive grating, which can always maintain the stable output of the single longitudinal mode (SLM) in theory. However, there are many types of die jumping phenomenon in the real laser, which is limited by the conventional mode hopping method, but can not effectively obtain the key information of the whole process of the die hopping. Through the OH-JTFA method, the full dynamic process of the die hopping is realized. In real time monitoring, the hopping process is presented directly by the time frequency waterfall graph, and all physical parameters of the transient process are obtained without distortion for the first time. The modulated chaotic EDFRL is a typical low dimensional chaotic system by introducing a degree of freedom to make the total light intensity chaotic output, and the output light field of the system contains a large number of dense longitudinal modes, when the total intensity of light is strong. The dynamic characteristics and evolution laws of each mode in the frequency domain are still unclear. By improving the resolution of the frequency domain of OH-JTFA, the time evolution characteristics of multiple parameters, such as single mode frequency, spectral line and light intensity, are extracted synchronously. It is found that when the total light intensity is low dimensional chaotic output, the frequency modulation and spectral lines appear in the frequency domain by a single mode. The important experimental results and innovation points in this paper mainly include the following three aspects: 1, the dynamic phenomena of a class of large degree of freedom nonlinear dynamical systems are found in a single FBG MLM-EDFRL by OH-JTFA method. The results show that the local mode produces the total. The frequency domain dynamic behavior that the light intensity can not present, including the mode self pulse, the pattern inverse phase dynamics, the chaotic multimode oscillation, the random multimode oscillation, and so on, uses the OH-JTFA method to obtain the time frequency waterfall diagram of the self organized feedback SLM-EDFRL typical model and the transient multimode oscillation evolution process for the first time. This method is the only method to achieve the synchronous extraction of EDFRL in SLM-EDFRL. The duration of die jumping, the distance and direction of the die, the number of modes involved in the competition and the frequency domain measurement of the model strength evolution, provide a more comprehensive observation method for understanding the mode instability and dynamic mechanism, which has important reference value.3. By improving the resolution of OH-JTFA in frequency domain, the pump modulation chaos is investigated. In the frequency domain dynamics of the optical fiber laser system, it is found that when the total light intensity is characterized by a typical low dimensional chaos, a large number of longitudinal modes in the frequency domain show very complex high dimensional dynamic characteristics. The nonlinear time series analysis of the modes shows that the mode with the chaotic characteristic and the pattern with random evolution characteristics are generally low. On this basis, the feasibility of using a large number of chaotic / random modes in the frequency domain of a chaotic fiber laser as a photon entropy source to generate multi-channel physical random codes is further discussed.
【学位授予单位】：国防科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN248

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