【作者】 张伟利；

【导师】 潘炜；

【作者基本信息】 西南交通大学 ， 通信与信息系统， 2008， 博士

【摘要】 上世纪八十年代起注入式半导体激光器(SL)受到了人们极大的关注,它们被广泛地应用在锁频、锁相、降低噪声、提高调制带宽、时钟恢复、微波生成和同步通信等领域。受到常规光反馈(COF)、共轭光反馈(PCF)等自注入和单/双向外部注入的SL,常呈现出丰富的动态特性。深入研究这些动力学行为,有助于揭示注入式SL这一典型非线性系统的物理本质,为提高SL工作性能、拓展其在光通信等领域的应用提供参考。另外,垂直腔面发射激光器(VCSELs)作为新型微腔SL的代表,较之传统边发射SL具有众多突出优点,但VCSELs特殊的有源区结构使其输出的偏振特性非常复杂,偏振自由度的引入导致注入条件下输出的非线性动态更加丰富,产生了许多新的课题和应用。因此,本论文对SL在光注入条件下的非线性动态和偏振特性展开深入研究,目的在于揭示光注入下SL的动态演变形式、偏振态分布规律和这些特性的物理成因,并探讨SL动态特性及偏振自由度等方面的控制措施和实际应用。处理方法上,基于自旋反转模型、速率方程和无量纲化处理方法,并采用Simulink多级封装技术,建立仿真模块;借助稳态分析、动力学分岔理论和小信号微扰理论等,并参考分岔图、频谱图、眼图、相空间轨迹、参数空间映射、相关性曲线等指标,来刻画输出的物理特性。研究的主要内容和结论有:综合考虑多次反馈和共轭镜响应时间等因素的影响后,对边发射SL输出分岔行为、光场时域信号对称性和噪声特性的研究表明:多次反馈使输出分岔提前,甚至改变倍周期和混沌状态的出现范围,并导致PCF条件下输出光场旋转π后不再对称;共轭镜响应时间对输出非线性和强度噪声都具有一定抑制作用,且响应时间越长抑制作用越明显;此外,基于PCF构建的同步通信系统,对共轭镜的位置不敏感,并对光纤传输中的色散和非线性效应具有一定消弱作用。采用不对称互注入和混合注入的新思想实现了SL的同步通信,并将前一思想发展到一对多和多对一的光网络通信中。仿真发现:引入不对称注入能够克服传统互注入系统不能进行混沌同步通信的缺点,确保两SL稳定的注入锁定同步;同步后,强弱两个注入方向上都表现出混沌滤波效应,可以实现双向通信。借助中间媒介引入单/双向混合注入,实现了两外部SL的类全同步混沌通信,该方法克服了传统同步系统中同步品质受编码影响以及信息的调制频率受混沌滤波限制不能大于弛豫振荡频率的缺点。详细分析了互注入VCSELs系统的偏振和动态特性,并将讨论拓展到强度不对称和含有附加反馈两种特殊情况。平行互注入时(注入光偏振方向与被注入VCSELs向同),两VCSELs表现出与光反馈相似的特点;垂直注入时(注入光偏振方向与被注入VCSELs垂直),频率失调可引起两VCSELs不同的偏振开关(PS)效应。以x偏振模式垂直注入为例,通过动态分析,发现两VCSELs输出存在一不对称区域,该区域内它们分别输出x和y偏振模式,互注入转变为单向注入。选择合适的互注入参数,还可以得到输出耦合模式近似周期性的模式跳变以及与之伴随的PS效应,数值模拟证实其物理原因为,具有最大增益的模式随参数的变化在x和y两个偏振方向上交替产生。利用时变垂直光注入的新方法来控制VCSELs的PS双稳特性,并推导了相应的数学模型,进行解释。时变注入对PS有推迟作用,注入系数变化越快,PS双稳区域越宽;物理上,PS的推迟作用源于输出对先前状态的记忆作用,推导的数学模型可很好地解释该特性。此外,论文首次针对VCSELs线性和椭圆两种输出偏振态,分析了其四波混频(FWM)效应和光电反馈下的动态特性。结果表明:线性偏振的FWM效应和光电反馈特性与边发射SL相似;椭圆偏振的FWM效应对于二色性和双折射参数非常敏感,介于正负弛豫振荡频率之间的共轭效率和再生效率的频谱通常会发生畸变;弱光电反馈引起椭圆偏振态直接分岔,强光电反馈使输出的两个线性偏振态呈现不同频率的同相或反相振荡。更多还原

【Abstract】 Since 1980s, optical injected semiconductor lasers (SL) have drawn much attention. They are widely used in frequency locking, phase locking, noise reducing, modulation width enhancement, clock recovery, microwave generation and synchronized communication etc. When subjected to self-injection, such as common optical feedback (COF) and phase conjugated feedback (PCF), or subjected to unidirectional and mutual injections from outer lasers, SLs tend to show rich dynamics. A detailed study on such behaviour can help us comprehending the essence of nonlinear systems of SLs, as well as enhancing the device performances and extending applications of SLs in optical communication. Besides, as a representative type of SL, vertical-cavity surface-emitting laser (VCSEL) shows lots of merits over traditional edge-emitting lasers (EELs). However, the polarization characteristics of a VCSEL is complex due to it’s special cavity configuration. The polarization degree of freedom adds more complex dynamics to optical injected VCSELs, generating new issues and applications. So this paper presents a detailed study on nonlinear dynamics and polarization characteristics of optical injected SLs. Our purpose is to expose the dynamical evolvement of SL, the law of polarization distribution and the related physical mechanism, and also to find ways of polarization dynamics control and some related applications.We develop simulation models by using multilevel masking method in Simulink. These models are found on the spin-flip mode, the rate equations and dimensioness method. In the analysis, steady state analysis, dynamical bifurcation and small perturbation theory are used; besides, bifurcation diagram, spectrum, eyediagram, track of phase space, mapping of parameter space, and correlation curve are taken as references to character output’s physical characteristics. The main contents and results of this thesis are:The bifurcation behaviors, symmetry of the time serial of optical filed and noise characteristics for EELs are analyzed, taking multiple feedback and response time of phase conjugate mirror in to consideration. The result show, multiple feedbacks will advance the bifurcation, or change the ranges of multiple period and chaotic states; optical field under multiple PCF is no longer symmetrical when rotated byπ; long response time of phase conjugate mirror suppresses nonlinearity and relative intensity noise. In addition, PCF can also be used in optical chaos communication as to reduce the dispersion and nonlinearity of the fibers.Novel ideas of asymmetrical mutual injection and multiplex injection are used for the first time to realize synchronized chaotic communication; the former are also extended for the use of one-to-many and many-to-one optical network communication. By using asymmetrical mutual injection, the disadvantage of temporary synchronization in traditional mutual injection system is overcome, and chaos-pass-filtering effect is shown in both directions, so we can communicate bidirectionally. By using multiplex injection introduced by an intermediary, the disadvantages, that encoding reduces synchronization degree and message frequency is constrained by chaos-pass-filtering, are avoided.The dynamics and polarization characteristics of mutually coupled VCSELs are investigated detailedly. In addition, the ways of using asymmetric mutual injection to control dynamics and polarization of VCSELs are discussed. Under polarization parallel mutual injection, the two VCSELs show similar characteristics as they were subjected to optical feedback. Under polarization orthogonal mutual injection, the two VCSELs show different polarization switching (PS) characteristics due to frequency detuning. Taking x-polaized mode orthogonal injection as an example, we find that there exists an asymmetrical region wherein the two VCSELs emit x-polarized and y-polaized mode respectively, and mutual injection turns into undirectional injection. Under certain parameter conditions, the compound mode of VCSELs shows almost periodical mode hopping with the company of PS, which is due to the maximal-gain mode generating alternatively in the x-polarized and y-polarized directions.PS bistability of VCSELs is controlled using a novel method of time-varying orthogonal injection, and a simple theoretical model is developed to explain the influence of time-varying injection. It is found that PS is postponed by time-varying injection, and the width of PS region is broadened by a fast scanning rate. Physically, this is due to the output’s memory about the former state, and it can also be well explained by the theoretical model. Furthermore, the thesis investigates, for the first time, four-wave-mixing (FWM) effect and optoelectronic feedback issue about VCSELs, taking both the linearly and elliptically polarized states into consideration. The results show, FWM of linearly polarized state is similar to that of EELs; FWM of elliptically polarized state are sensitive to anisotropy and birefringence parameters, especially, when frequency detuning is between positive and negative relaxation oscillations frequency, the regenerated and phase conjugated spectra show evident distortions. Weak optoelectronic feedback induces bifurcation of the elliptically state, and strong optoelectronic feedback adds in-phase and anti-phase fluctuations with different frequencies to the two linearly polarized states.更多还原