【作者】 赵慧；

【导师】 柴路；

【作者基本信息】 天津大学 ， 光电子技术， 2010， 硕士

【摘要】 近二十多年来,锁模光纤激光器以其小巧的体积、优越的性能、灵活的结构和丰富的锁模机制,成为超短脉冲激光技术中一个极具活力和应用前景的分支领域,受到了人们的广泛关注。近年来新提出的全正色散(ANDi)锁模光纤激光器,由于不含有负色散元件,因此结构可以更为简单。同时,它主要依靠频谱滤波效应等耗散过程实现腔内脉冲的整形,因此又为锁模光纤激光器引入了新的锁模机制。本文围绕掺镱的ANDi锁模光纤激光器开展了相关的理论、数值和实验研究工作。理论研究方面,本文较为详细的阐述了光纤激光器中色散、非线性和增益三个关键要素对于脉冲的影响,并在此基础上推导得到了描述锁模光纤激光器中脉冲传输特性的Ginzburg-Landau方程。同时阐述了ANDi锁模的具体机制及其锁模脉冲的特点。数值模拟方面,建立了锁模光纤激光器的数学模型,利用分步傅立叶方法数值求解。在形成清晰的腔内动力学过程图像的基础上,分别讨论了短腔和长腔两种条件下,腔中单模光纤长度对于锁模脉冲特性的影响,以及长腔条件下光纤增益对于输出脉冲特性的影响。实验方面,搭建了基于传统单模光纤的环形腔的掺镱ANDi锁模光纤激光器,分别在26.6MHz、6.66 MHz、5.05 MHz的重复频率下得到了3.5nJ、12nJ和20nJ的单脉冲能量,通过优化增益光纤长度,又进一步将5.05 MHz重复频率下的单脉冲能量提高到了32nJ,并利用光栅对对此时的高啁啾宽脉冲进行了腔外压缩实验,取得了初步成效。实验中观察到的腔长变化时脉冲参数的变化趋势与数值模拟的结果一致。更多还原

【Abstract】 During the past two decades, mode-locked fiber lasers have been developed to be a promising branch of ultrashort pulse laser technologies due to their compact sizes, superior performances, flexible structures and diverse mode-locking mechanisms, causing wide-spread academic and applicational interests. The recently proposed all-normal-dispersion (ANDi) mode-locked fiber lasers have even simpler structures due to the exclusion of negatively dispersive intracavity elements, and introduce a new mode-locking mechanism into mode-locked fiber lasers with their dissipative-process-dependant shaping of intracavity pulses, the key of which is the spectral filtering effect. In this thesis, theoretical, numerical and experimental research concerning this novel kind of mode-locked fiber lasers has been demonstrated.The theoretical research started with a fairly detailed illustration of how the three key features of a fiber laser, containing dispersion, nonlinearity and gain, affect the optical pulse individually. Based on this, the Ginzburg-Landau equation which describes the propagation of optical pulses inside a mode-locked fiber laser was derived. Also the specific mechanism and the pulse properties of the ANDi mode-locking regime were discussed.Numerical simulations were performed using the split-step Fourier method for the ANDi mode-locked fiber laser. A clear image of the intracavity dynamic process was achieved, which was followed by a discussion of how the output pulse characteristics change when the length of the intracavity single-mode fiber was altered. The impact of the fiber gain on the output pulse properties was also discussed.A ring-cavity Yb-doped ANDi mode-locked fiber laser was experimentally constructed. Single pulse energies of 3.5nJ, 12nJ and 20nJ were obtained when operating at repetition rates of 26.6MHz, 6.66 MHz and 5.05 MHz, respectively. The energy of the 5.05 MHz-repetition-rate pulse was further increased up to 32 nJ by optimization of the gain fiber length, and the extracavity compression was performed utilizing a grating pair. The experimentally observed variation tendency of output pulse parameters with the change of total cavity length was in agreement with simulation results.更多还原