【作者】 赵羽；

【导师】 刘永智；

【作者基本信息】 电子科技大学 ， 光学工程， 2009， 博士

【摘要】 超短脉冲光源不仅可作为未来超高速、大容量、长距离光纤通信系统的理想光源，而且是研究非线性、超快等现象的重要工具。光纤激光器具有体积小、重量轻、增益特性好、转换效率高、阈值低、输出光束质量好、与现有通信系统相兼容等特点，是目前超短脉冲激光技术领域中的热点研究课题。本论文围绕锁模光纤激光器，以掺Er³⁺被动锁模激光器为研究重点，对激光器系统中亟待解决的光谱边带和荧光的抑制、耦合输出比与偏振控制器的优化、重复频率的提高和控制、高能量脉冲输出和脉冲稳定性的保持等问题，展开相应的理论和实验研究，并对其在超宽带无线通信中的应用进行了研究，具体工作包括：1．对比分析了主动锁模、被动锁模和混合锁模等锁模技术的优缺点，研究了锁模光纤激光器的工作原理。结合速率方程和非线性薛定谔（Nonlinear Schr（o｜¨）dinger,NLS）方程，建立了既能描述泵浦光子与信号光子之间的相互作用和粒子数浓度变化，又能分析光纤的色散和各种非线性效应的锁模光纤激光器模型。并基于该模型研究了不同参数下锁模信号、泵浦功率和ASE（Amplified Spontaneous Emission）光功率沿光纤纵向的传输情况。2．基于上述模型，结合掺铒光纤中荧光的产生机理，研究了锁模光纤激光器中抑制ASE光和可见荧光的产生，提高泵浦效率、优化激光器的方法。并进行了非线性偏振旋转被动锁模光纤激光器的实验研究，获得了重复速率15．9MHz，单脉冲能量15．75pJ，脉冲宽度约500fs的锁模光脉冲。3．通过NPE被动锁模光纤激光器的理论仿真和实验结果的对比分析，详细研究了激光器腔体环长、增益光纤长度、耦合输出比等关键因素对光谱边带的和脉冲稳定性的影响，得出了抑制光谱边带的方法。对比分析了九种耦合输出比的实验结果，得出了使脉冲波动小、谱宽宽和脉冲能量大的各种最佳耦合输出比值。耦合输出比为70％时单脉冲能量达3．86nJ。实验最终获得了光谱边带抑制较好、重复频率15．87MHz、单脉冲能量0．52nJ的稳定脉冲激光。4．设计了一种基于磁光晶体法拉第旋光效应的电控式偏振控制器，既继承了电控式偏振控制的优点，又简化了控制电路的复杂性，降低了器件的制造成本，并实验研究了其技术可行性。实验结果表明，该偏振控制器的偏振旋控制能力和线圈电流强度之间并不是一个线性的关系，若要通过此类偏振控制器获得精确到1度的偏振旋转控制，电流源电流强度的调节能力需要精确到0．01A的量级。5．实验研究了高耦合输出比下，泵浦功率、耦合输出比与偏振控制器的调制相结合控制重复频率的方法，研究了耦合输出比为40％到90％间时不同谐波锁模状态下锁模光纤激光器光谱和脉冲的变化情况。并研究了耦合输出比为70％、80％和90％时出现的孤子簇现象。6．设计了一种基于有源副腔的被动锁模光纤激光器，并进行了无源、有源副腔锁模光纤激光器的实验研究。利用NPE型被动锁模光纤激光器的基阶锁模状态保证脉冲的稳定性，通过主腔与副腔腔长比例的恰当选择，将基阶锁模光脉冲重复频率提高了27倍（从12．9MHz提高到349MHz），并通过主腔谐波锁模与有源副腔的结合获得了GHz级别的被动锁模光脉冲输出。7．对被动锁模光纤激光器在超宽带（Ultra-Wide Band（UWB））无线通信中的应用进行了探索性实验研究。基于锁模脉冲色散展宽原理，在不需要使用高速调制器和腔外调制信号的情况下，获得了符合FCC（US Federal CommunicationsCommission）室内UWB无线传输规定的光子超宽带脉冲源。并结合被动谐波锁模技术和有源副腔技术，进行了多重复频率光子超宽带脉冲源的实验研究。8．利用啁啾脉冲补偿无线信道色散效应的原理，基于超短脉冲光纤激光器，宽带光电转换器，放大器和Bowtie孔径超宽带天线，进行了UWB室内无线传输实验研究。对应无线传输发射端前加和不加电脉冲放大器的两种情况，经过UWB室内无线传输后分别探测到了高斯单周脉冲（FWHM约150ps）和高斯偶脉冲（FWHM约120ps）。通过分析天线间距，电磁干扰，光脉冲源，以及衰减器和放大器对UWB室内无线传输的影响，得出了这种系统的最佳结构。更多还原

【Abstract】 The generation of ultra-short pulses is not only the best source of ultra-fast, bigcapacitance, and long distance fiber communication system, but also the front edgeresearch about nonlinear optics and ultrafast optics. Fiber laser offer a number ofadvantages including small volume, light weight, compact structure, high stability, goodgain features, high conversion efficiency, low threshold, high beam quality andcompatibility with fiber-optic communication system. Now it has become one of thehottest topics in the field of the ultra-short pulse lasers. This paper takes Er³⁺ dopedpassively mode-locked fiber laser as the research keystone, made research on thefluorescence and side bands depressing methods, output ratio and polarization controloptimization, repetition rates increase technology, high energy pulse output, stability ofthe pulse and its use in UWB wireless communication, which include1. The advantages and disadvantages of actively mode-locking, passivelymode-locking and mixed mode-locking technologies have been analyzed. The physicalmechanism of mode-locking in the fiber laser was investigated. A novel model ofmode-locked fiber laser was developed by combining the rate equation of Er³⁺ dopedfiber and Nonlinear Schr（o|¨）dinger （NLS） equation. Investigation was made on thelongitudinal propagation characteristics of pump, mode-lock signal and AmplifiedSpontaneous Emission （ASE） power along longitudinal fiber with the proposed model,2. With the proposed mode and the emission mechanism of the fluorescence in highenergy pulsed fiber laser, the methods of effectively depressing the fluorescence andimprove the pump efficiency have been discussed. The Nonlinear PolarizationEvolution （NPE） passively mode-locked fiber laser experiments have been carried out.Mode-locked pulses with repetition rates of 15.9MHz, single pulse energy of 15.75pJand pulse width of 500fs have been obtained.3. Based on the comparing of numerical emulation and experiments of NPEpassively mode-locked fiber laser, the effects of different EDF lengths, different ringlengths and different output ratios on spectrum sidebands and pulse stability wereanalyzed. The ways of side bands depressing were obtained. Experiments with 9 kinds of output ratios on pulses quality were carried out, on which we summarized the ratioscorresponding to smaller fluctuation, larger single pulse energy, and wider spectrumwidth. And the single pulse energy would be the largest one （about 3.86nJ） whenR=70%. The output pulses with restrained side bands, the repetition rate of 15.87MHz,and the single pulse energy of 0.52nJ have been obtained.4. A new polarization control （PC） method was proposed based on Faraday opticsrotation mechanism in opto-magnetism crystal. This PC not only inherits theadvantages of electrical PC but also simplifies the complexity of circuits and save thecost of manufacture apparatus. The technology feasibility of this PC was experimentalcarried out, which prove that the polarization control ability of this PC is not linearitywith current intensity in the loop, the modulation ability of current intensity should beas precise as 0.01 A if we want to get the polarization control ability as precise as 1°.5. The ways of repetition rates control based on the modulation of pump power,output ratio and polarization controller were experimental carried out when the outputratios were high. The fiber laser spectrums and pulses in different harmonicmode-locking states were analyzed when the output ratios were between 40% and 90%.The compound bound pulse soliton states of fiber laser were also studied when theoutput ratios were 70%, 80% and 90%.6. A novel structure of passively mode-locked fiber laser was presented at highrepetition rates with an active slave ring cavity connected to a NPE master cavity.Based on the stable basic mode-locking state, the NPE mode-locked pulses wereinjected into the active slave cavity, and the ratio of master cavity length and slavecavity length was carefully modulated in order to achieve self-starting injectionmode-locking. Twenty-sevenfold evolution of repetition rates in NPE passivelymode-locking pulse was obtained at the basic mode-locking rank, from 12.9MHz to349MHz. And GHz rates were obtained from the slave cavity based on differentharmonic locking orders of the master cavity.7. A novel method for UWB （Ultra-Wide Band） microwave signal generation usinga passively mode-locked fiber laser is proposed and demonstrated. Er³⁺ deeply dopedfiber as long as 3m was used to get enough dispersion of fiber in order to make thepulse width wider to accord with FCC （US Federal Communications Commission）criterion about UWB wireless transportation in door, without using any high speed modulator or signal. Based on the principle of harmonic mode-locking and active slavecavity, 12 different kinds of UWB pulse periods were obtained.8. Experiments study of UW over fiber wireless transportation indoor was carriedout based on passively mode-locked fiber laser, technology of UWB optoelectronicconversion, UWB pulse amplifier and Bowtie aperture UWB antenna technology.Corresponding to amplified or not, gauss monocycle pulse （with FWHM of 150ps） ordoublet pulse （with FWHM of 120ps） was detected after UWB wireless transportationindoor. The influences of antennas distance, electromagnetic wave indoor disturbance,optical pulse source, attenuator and amplifier were studied in order to get the beststructure of this kind of system.更多还原