【作者】 张程；

【导师】 柴路； 宋有建；

【作者基本信息】 天津大学 ， 光学工程， 2013， 硕士

【摘要】 光纤激光器因其紧凑的结构、灵活的腔型、丰富的色散和非线性效应、优越的输出性能，近年来成为了超短脉冲领域研究的新宠儿，并在消费类电子产品、机械制造、生物成像、医疗保健、信息技术和军事国防等领域，发挥着越来越多、也越来越重要的作用。本文对掺铒光纤锁模激光器开展了大量数值模拟和实验研究。这里，掺铒增益光纤是腔内唯一具有正常色散的部分，通过单模光纤引入反常色散，我们构造出了谐振腔色散图分布，目的是通过优化谐振腔的设计，从而在色散管理孤子掺铒光纤锁模激光器中得到宽光谱、窄脉冲。主要工作包括：1、探索谐振腔长度对脉冲窄化特性的影响。实验上，应用不同掺杂浓度的铒光纤，搭建了一台结构紧凑的锁模激光器，利用非线性偏振旋转锁模机制，实现稳定的自启动锁模运转；通过调节单模光纤及增益光纤长度来调节激光器的增益、色散、非线性参数，旋转波片角度控制等效可饱和吸收的调制深度，分别获得三种色散域（净负色散、近零色散和净正色散）的稳定锁模运转；比较分析了高掺杂、强增益短光纤对获得高重复频率、窄脉冲、宽光谱脉冲的优势。2、谐振腔的非线性效应增强实现激光器的脉冲窄化。提出在激光腔内引入一段零色散光纤的方法，以保证激光器泵浦、增益和净色散量不变的条件下，仅仅通过提供非线性效应进一步展宽光谱，获得窄脉冲；从数值模拟和实验验证两方面，讨论零色散光纤的放置位置和长度参数对腔内脉冲动力学过程的影响，得出结论：在激光器单脉冲锁模运转的范围内，在增益光纤后增加越长的零色散光纤能够获得越宽的光谱，相应的变换极限脉冲宽度也越窄。3、讨论谐振腔输出位置对直接获得窄脉冲输出的影响。基于优化后、带有零色散光纤的、近零色散域锁模光纤激光器，通过调节输出位置前后两段单模光纤的长度，以移动输出位置，使腔内最宽光谱和最窄脉宽得以输出腔外，最终得到直接输出脉冲宽度为55fs，光谱宽度为141nm的超短脉冲输出。更多还原

【Abstract】 Fiber lasers have always been of fundamental interest in the past few decades forits feature of compact size, flexible cavity, abundant dispersion and nonlinear effects,low cost, and high stability. Generation of ultra-short pulses through fiber lasers hasappealed considerable attention to the field of consumer electronics, mechanicalmanufacture, bio-imaging, medicine, telecommunications, and the military anddefense industry.In this paper, we mainly focused on the dispersion-managed soliton laser basedon Erbium-doped fiber. Here, Er-doped fiber had normal dispersion. We utilizedsingle mode fibers to induce abnormal dispersion so that the laser cavity was builtwith dispersion map. In this way, we can achieve short pulses through optimizing thecavity design. The main subjects were summarized in the following outline:1、 Exploring the effect of cavity length on pulse shortening.We experimentally built up a compact-sized ring-cavity fiber laser with passivelymode-locking mechanism of nonlinear polarization rotation. By stepwise alteringthe length of active fibers and single mode fibers, and properly adjusting thepolarization of wave plates, mode-locking operation with three differentdispersion regimes were achieved. Then, comparing two kinds of Er-doped fiberswith drastically different doping concentrations, we obtained the advantages ofhighly Er-doped fiber lasers working in the vicinity of zero dispersion.2、 Gaining pulse shortening via increasing nonlinear effects within cavity.We investigated the effects of a piece of zero dispersion fiber on the pulsedynamics in a passively mode-locked fiber laser operating in stretched-pulseregime. Numerical simulation suggests that proper location and length of the zerodispersion fiber facilitates spectrum broadening and pulse shortening in fiberlasers while keeping a constant of net cavity dispersion. A nonlinear polarizationevolution mode-locked Er-doped fiber laser with dispersion map is built based onthe simulation. Larger optical spectrum broadening can be obtained by insertionof a longer zero dispersion fiber after the active fiber in single pulse operation,which agrees with the simulation very well. 3、 Directly obtaining ultra-short pulses with output port position optimized.By the means of varying the position of output port, the ultra-short pulses can beachieved directly without any dispersion compensation. As a result, weexperimentally adjust the length of the two segments of single mode fibers beforeand behind output port respectively, and got the output position optimized.Ultimately,55-fs,141-nm pulse train was gained directly from the output port.更多还原