【作者】 何理；

【导师】 杨伯君；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2007， 博士

【摘要】 本论文的工作分为两个部分，前一部分研究了双泵浦主动锁模光纤激光器的研制，利用Sagnac干涉环对脉冲的压缩以及Sagnac干涉环多波长光纤激光器的研制。后一部分讨论了光子晶体光纤在有源器件中的应用。光子晶体光纤是二氧化硅-空气微结构光纤。由于它在色散与非线性诸多方面具有普通单模光纤没有的特性，它能在一个较宽的频带内保持单模特性，它的零色散点可以在800nm～1600nm之间变化，它的纤芯可以比较小而产生较大的非线性，γ值在850nm处可达到240W^-1．km^-1。故从1996年第一根光子晶体光纤出现就引起人们广泛的兴趣。但由于其单价目前还比较昂贵，损耗也比单模光纤大，要在近期利用光子晶体光纤代替常规单模光纤进行长距离传输是不可能的。但利用它做成有源器件，在光通信中，特别是波分复用系统中使用是很有前途的，如宽带色散补偿、光脉冲压缩、波长变换、超连续谱产生和光放大等。本论文在深入研究光子晶体光纤特性基础上，对光子晶体光纤在脉冲压缩，超连续谱产生和光子晶体光纤中参量放大进行深入研究。本论文的主要工作如下（黑体部分为创新性工作）：研制了双泵浦10GHz锁模掺铒光纤激光器，简要的回顾和总结了实现超短脉冲压缩方法，从实验上实现了利用Sagnac干涉环对脉冲的压缩。利用Sagnac干涉环的开关特性，环中低能量的噪声被Sagnac干涉环反射回去，有效消除噪声、改善脉冲质量。在多波长光纤环激光器中，通过控制偏振控制的器可以方便实现双波长和三波长激射。双波长激射时，激射波长分别为1558.78nm和1559.02nm，相应的3dB带宽分别为0.018nm和0.019nm。三波长激射时，中心波长分别为：1558.61nm、1558.76nm和1559.03nm，3dB带宽相应为0.02nm、0.016nm和0.026nm。实验中还发现，随着激射波长数的增加，激射波长的稳定性降低。详细介绍了光子晶体光纤的几个突出优点：单模传输特性、高非线性效应、可控色散特性和双折射特性。在此基础上，讨论了光子晶体光纤在有源器件中的应用，同时介绍了它在各应用领域中的优势。利用小纤芯光子晶体光纤构建的光纤激光器，在同等泵浦条件下，该光纤更容易产生非线性效应，在研制激光器时不仅可以节约光纤而且可以在很大程度上降低泵浦条件，这对于激光器的实用化和商业化是十分有利的。在我们的研究成果中，国内首次在光纤环激光器的环形腔中引入一段色散和非线性系数分别为164ps／（nm．km）和36W^-1．km^-1的光子晶体光纤，利用孤子压缩得到窄脉宽、大谱宽的脉冲输出。同时，估算了相应的脉冲为基阶孤子输出。系统分析了自相位调制、四波混频和受激拉曼散射等因素对光子晶体光纤中超连续谱产生的影响。在国内首次利用50MHz被动锁模光纤环激光器为光源，正色散平坦光子晶体光纤为非线性介质，利用光纤的非线性效应进行超连续谱产生的实验。实验结果表明：对锁模激光器输出的1.6ps脉冲经掺饵光纤放大器放大后注入光子晶体光纤，得到20dB带宽超过237nm的超连续谱。同时对皮秒脉冲致超连续谱产生的因素进行了分析。采用被动锁模光纤环激光器做为光源，色散平坦光子晶体光纤为非线性介质，利用光纤的非线性效应进行超连续谱产生的实验。利用该激光器高功率输出端口产生的689fs，1550nm的锁模脉冲注入一段40m长的光子晶体光纤，获得20dB谱宽达439nm的超连续谱。利用该激光器波长可调谐的特性，从实验上获取不同泵浦波长下超连续谱的产生。从理论上分析了光子晶体光纤参量放大器的增益特性和带宽特性，找出光子晶体光纤的非线性系数和色散等参数对参量放大的增益和带宽的影响，其数学模型采用由非线性介质中光的传播方程导出的耦合波方程。然后，利用一段色散平坦光子晶体光纤构建了光纤参量放大器，实现了参量放大和3dB带宽范围内最大转换效率约为-26dB波长转换。更多还原

【Abstract】 The research work in this dissertation covers both fiber ring laser and applications of photonic crystal fiber in active devices. For fiber ring laser, dual-pump mode-locked erbium-doped fiber ring laser, as well as compressing optical pulse by using Sagnca interferometer, is demenstrated. Also, a switchable multiwavelength fiber ring laser with Sagnac interferometer has been developed. As far as photonic crystal fiber is concerned, it is the fiber with a periodic microstrucure in air-glass. Compared with conventional single-mode fiber, PCF has some unique characteristics such as controllable dispersion and high nonlineatity. It can support endlessly single mode over a broad spectral range, as well as the zero-dispersion wavelength can vary from 800nm to 1600nm. PCF has high level of nonlinieatity due to the small core diameter, and values as high asγ=240W^-1. km^-1 at 850nm have been reported. Since the first PCF is invented in 1996, it has gained intense attention. For the expensive price and high loss compared with conventional single-mode fiber, it is impossible for long distance transmission in take place of conventional fiber. However, active devices based on PCF can expect a series of new applications in optical communication such as broadband dispersion compensation, optical pulse compression, wavelength conversion, supercontinuum generation and optical amplification. Based on the analysis of characteristics of PCF, applications of PCF in pulse compression, supercontinuum generation and parametric amplification are investigated in detail. The research works in the dissertation are summerized as follows:10GHz dual-pump mode-locked erbium-doped fiber ring laser is demonstrated. The schemes of ultrashort pulse compression are reviewed and summarized briefly. Pulse compression using Sagnac interferometer has been experimentally studied. According to the switching characteristics of Sagnac interferometer, the noise with low energy can be reflected by the Sagnac interferometer. Thus, it is helpful to eliminate the nosie and improve the qulity of pulse. For switchable multiwavelength fiber ring laser, the laser can be designed to operate in dual-wavelength or triple-wavelength mode and the lasing mode can be controlled by a polarization controller. Dual-wavelength operation at 1557.78nm and 1559.02nm can been obtained. The corresponding 3dB bandwidth is 0.018nm and 0.019nm. Also, triple-wavelength operation at 1558.61nm, 1558.76nm and 1559.03nm can be observed. And the corresponding 3dB bandwidth is 0.02nm, 0.016nm and 0.026nm. Moreover, it is found that the lasing is less stable when the numbers of lasing lines increase.Several prominent merits of PCF, such as property of single mode transmission, high nonlinearity, controllable dispersion and birefringence are systematically reviewed. Also, applications of PCF in active devices and potential advantages are introduced.For fiber ring laser based on PCF, it can largely improve the pump efficiency for same pump power compared with convential fiber and reduce the fiber length because PCF has high level of nonlinieatity due to the small core diameter. It is helpful to meet the practical and commertical demands. In our research work, PCF with dispersion parameter of 164ps/（nm. km） and nonlinear parameter of 36W^-1. km^-1 are introduced into the fiber laser and narrow pulse trains with broad spectrum can be obtained by soliton compression effects. Also, the output pulse is estimated as fundmental soliton.Several factors contributing to supercontinuum generation （SC）, such as self-phase modulation （SPM）, four-wave mixing （FWM） and stimulated Raman scattering （SRS）, are analyzed in detail. By using 50MHz mode-locking fiber ring laser, SC can be obtained from dispersion-flattened PCF. The bandwidth of 237nm （at 20dB level） is achieved by launching 1.6ps pulses into a section of PCF. Moreover, the processes underlying spectral broadening are analyzed.By using passively mode-locking fiber ring laser, SC can be obtained from dispersion-flattened PCF. The results show that bandwidth of 439nm （at 20dB level） can be achieved by launching 689fs pulses into a section of PCFs. SC at different wavelength can be obtained by tuning the pump wavelength of the passively mode-locked fiber ring laser.The gain characteristics and bandwidth of optical parametric amplifiber （OPA） based on PCF are addressed theoretically. The relationship between the properties of PCF, such as nonlinearity and dispersion, and characteristics of OPA are analyzed. The modal is based on coupled equations derived from transmission equations of lightwave. Then, we propose an OPA based on PCF. The results show that maximum conversion efficiency is about -26dB.更多还原