【作者】 杨旭；

【导师】 杨昌喜；

【作者基本信息】 清华大学 ， 光学工程， 2010， 硕士

【摘要】 超短脉冲光纤激光光源由于其性能优越、价格低廉、结构紧凑、设计灵活,在光纤通信、光纤传感、精密加工、生物医学相关领域具有重要的应用。锁模器件是光纤激光器中获得超短脉冲的关键元件。本论文主要研究了非线性偏振旋转和利用波导阵列两种锁模机制,从理论分析、数值模拟和实验研究几个方面进行了探讨。其主要内容如下:1.论文简要回溯了光纤激光器的发展历程,介绍了主动、被动锁模机理,着重介绍了被动锁模光纤激光器的研究现状。2.分析了光纤激光器的工作原理。搭建了基于非线性偏振旋转的锁模光纤激光器,获得了较为稳定的连续锁模脉冲序列。其重复频率21.47MHz,脉宽670fs,中心波长位于1560nm的光谱-3dB带宽6nm。研究了孤子频谱边带,并观察到调Q、调Q锁模、多次谐波锁模等多种输出状态。3.引入决定波导阵列中现象的方程组,分析了在特殊条件或采取近似条件下,波导阵列中存在的离散衍射和离散自聚焦两种效应,并通过数值模拟得到了证实。另外通过数值模拟得到了不同参数的波导阵列对于超短脉冲的整形的效果影响。4.设计并联系加工了AlGaAs材料的波导阵列。其后搭建了一套测量波导阵列对超短脉冲压缩的实验装置,用自相关仪对超短脉冲经由波导阵列前后的脉宽进行测量。同时分析了实验中的损耗来源。5.回顾了整个论文工作,指出波导阵列与光纤的耦合是其应用于光纤激光器锁模的关键问题,提出了降低损耗的方案,供今后的研究工作参考。更多还原

【Abstract】 Due to their superior performance, low cost, compact and flexibility, ultra-short laser sources have important applications in fiber communication, fiber sensors, precision machining, biomedical and related areas. The mode-locking device serves as the key factor in generating ultra-short pulses. In this dissertation, we mainly focused on two mode-locking mechanisms, nonlinear polarization rotation and by waveguide arrays. Theoretical analysis, numerical simulation, as well as experimental investigation have been carried out. This dissertation includes:1. We briefly reviewed the history of fiber lasers and introduced active and passive mode-locking mechanisms. We emphasized on the present research of passively mode-locked fiber lasers.2. The operation mechanism of fiber lasers was analyzed. Then we built up a mode-locked fiber laser based on nonlinear polarization rotation. Stable continuous mode-locked pulses were generated, which had a 21.47MHz repetition rate, a 670 fs pulse width and a 6nm -3dB spectrum width centered at 1560nm. The soliton spectrum sideband was studied. We have also observed the phenomenon such as Q-switching, Q-switched mode-locking and different times of harmonic mode-locking in this fiber laser.3. We introduced the equations that determine the phenomenon in waveguide arrays. Two effects in waveguide arrays, discrete diffraction and discrete self-focusing, were studied and proved by numerical simulations respectively. Further we have investigated the influence of waveguide arrays’parameter on ultra-short pulse reshaping.4. We designed the blue print of waveguide arrays and have them manufactured. Then we built up an experimental device for measuring the ultra-short pulse reshaping in waveguide arrays. We measured the width before and after the pulse through the waveguide arrays. The loss in the experiment is analyzed. 5. Summarized the whole dissertation. The decoupling between waveguide arrays and fibers was the key issues for their applications in mode-locked fiber lasers. Some suggestions to lower the loss were proposed for future research reference.更多还原