【作者】 伍波；

【导师】 刘永智；

【作者基本信息】 电子科技大学 ， 光学工程， 2007， 博士

【摘要】 窄线宽光纤激光器在超远距离传感和高精度光谱方面有广泛的应用。特别是作为光纤激光传感器，它具有对电磁场的抗干扰、安全、体积小、可远程控制等特性，并且由于它的高灵敏度以及利用WDM技术实现多路传输，在军事上也有很大的应用潜力。本文针对新型结构的环形腔和线形腔掺Er³⁺窄线宽光纤激光器的选模器件、腔形设计、测量方法等相关问题，展开相应的理论与实验研究。论文的主要工作包括：1．概述了激光器的线宽理论。对延迟自外差／零差激光线宽测量方法进行了误差分析。讨论了相干因子、延迟光纤倍数、以及延迟光纤长度对延迟自零差线宽测量结果的影响。讨论了延迟光纤倍数、以及延迟光纤长度对延迟自外差线宽测量结果的影响。并分析了最小二乘曲线拟合谱线的线宽对测量线宽的影响。采用延迟自外差方法测量了一只DFB半导体激光器的线宽。2．对掺Er³⁺窄线宽光纤激光器的进行了理论分析。分别讨论了掺Er³⁺光纤激光器的输出特性以及窄线宽光纤激光器的设计方案。并利用光纤光栅法布里-珀罗标准具理论，分析了光纤光栅标准具随腔长变化的性质、光纤光栅标准具随光栅反射率变化的性质。3．进行了以光纤光栅法布里-珀罗标准具为外腔选模器件的环形腔单频光纤激光器实验研究。使用光纤环行器的环形腔光纤激光器获得9.2mW的激光输出，斜效率约为7％，输出激光3dB线宽为0.01nm，信噪比为50dB。在光纤耦合器结构的环形腔光纤激光器中得到输出单频光功率为42mW，斜率效率为33％。分析了两种方案输出特性不一致的原因。4．进行了1535nm线型腔光纤激光器实验研究，以布拉格波长为1535nm的光纤光栅F-P标准具为选模器件，使用了全光纤结构的法拉第旋转器来抑制空间烧孔效应。激光器阈值抽运光功率为12mW，最大输出信号光功率为39.5mW，单端最高输出信号光功率为22mW，斜率效率为29.7％。激光器输出中心波长为1534.83nm，光谱稳定，信噪比高。采用15km单模光纤延迟线进行了延迟自外差线宽测量，得到光纤激光器的3dB线宽小于7.5kHz。5．进行了高功率线型腔光纤激光器实验研究。光纤激光器主要由两个中心波长1550nm的光纤光栅F-P标准具（FBG F-P）和高掺Er³⁺光纤线形腔构成，阈值抽运光功率为11mW，输出信号光功率为73mW，斜率效率达55％。激光器输出中心波长为1550nm，光谱稳定，信噪比高。采用10km单模光纤延迟线进行了延迟自外差线宽测量，得到光纤激光器的3dB线宽小于10kHz。6．进行了窄线宽光纤激光器的温度稳定性实验研究。光纤激光器当抽运光功率为200mW时，得到50mW输出信号光功率，激光器斜率效率为27％。采用10km单模光纤延迟线进行了延迟自外差线宽测量，得到光纤激光器的3dB线宽小于10kHz。信噪比为56dB。在温度稳定性实验中，当温度从25℃变化到90℃时，激光器的输出波长变化了1.02nm，光纤光栅的温度灵敏度为0.016nm/℃。在温度变化中，激光器的输出功率略有波动，输出激光波长连续变化，无跳模现象，自外差谱线的3dB带宽的变化小于1kHz。7．系统理论分析光纤饱和吸收体压窄光纤激光器线宽的机理。采用环形行波腔结构，将光纤光栅法布里-珀罗标准具作为主要选模器件，以较短的低损耗光纤饱和吸收体稳频，构造了高效的环形行波腔单频光纤激光器。实验中得到了稳定的单频激光，无跳模现象发生，输出信号光功率为39mW，斜率效率为30％，信噪比大于50dB，测量激光线宽小于10kHz。更多还原

【Abstract】 Narrow linewidth fiber laser has great applications for extremely long-range sensors system and high resolution analysis system of optical spectrum. Especial as fiber laser sensor, it has particular characteristics of safety, remote controller, small bulk and anti-electromagnetic disturbance. It has potential application for defence due to its high sensitivity and the feasibility of multiplex transmission using WDM technology. This thesis is mainly concentrated on the devices of mode selection, design of cavity and measurement method of linewidth in the Erbium-doped narrow linewidth fiber laser. Theoretical analysis and the experiments are both studied.The main results are as follows:1. Theory of laser linewidth has been summarized. Analyses of measurement error of self-heterodyne/homodyne methods have been studied. The influence of coherence factor, multiple of coherence length and the length of delay fiber to the result of measurement have been discussed in the self-homodyne method. The influences of multiple of coherence length and the length of delay fiber to the result of measurement have been discussed in the self-heterodyne method also. The influence of least squares curve fitting algorithm to the result of measurement has been analyzed too. The linewidth of a DFB semiconductor laser has been measured by the delayed self-heterodyne method.2. The model of Erbium-doped fiber laser has been analyzed theoretically. The output characteristic has been illustrated and the scheme of the Erbium-doped fiber laser has been designed. The variations of the performance of the fiber Bragg grating Fabry-Perot etalon with the length of the cavity and the reflection coefficient of fiber Bragg grating have been discussed, according to the theory of fiber Bragg grating Fabry-Perot etalon.3. The experiments of single frequency fiber ring laser with mode selection by fiber Bragg grating Fabry-Perot etalon have been performed. About 9.2mW output power and 7% slope efficiency are obtained in the experiment of fiber ring laser using fiber circulator. The 3dB linewidth of fiber laser is less than 0.01nm. In the experiment of fiber ring laser using fiber coupler, single frequency output power is 42 m W and the slope efficiency attain to 33%. The difference in output characteristic of the two fiber ring laser has been analyzed4. The experiment of 1535nm fiber laser with linear cavity has been carried out, in which, the fiber Bragg grating Fabry-Perot etalon with the Bragg wavelength of 1535nm is used as mode-selecting device, and the fiber Faraday rotator is used to restrain the spatial hole burning effect. Stable single frequency 1534.83 nm laser is acquired. The fiber laser exhibits 12 mW threshold. Total 39.5 mW output power and one end 22 mW output power are obtained. Optical-optical efficiency is 27% and slope efficiency is 29.7%. The 3dB linewidth of laser is less than 7.5 kHz, measured by the delayed self-heterodyne method with 15 km monomode fiber.5. A high output power narrow linewidth fiber laser based on fiber Bragg grating Fabry-Perot etalon has been accomplished. The fiber laser is composed of two 1550nm fiber Bragg grating Fabry-Perot etalons and high Er³⁺-doped fiber linear cavity. Stable single frequency 1550nm laser is acquired. Pumped by two 976nm laser Diodes, the fiber laser exhibits 11mW threshold. 73mW output power is obtained. The slope efficiency is 55%. The 3dB linewidth of laser is less than 10 kHz, measured by the delayed self-heterodyne method with 10km monomode fiber.6. The experiment on the stability of laser linewidth has been performed. The fiber laser exhibits 1 lmW threshold. 50 mW output power is obtained upon the 200 mW pump power. The slope efficiency is 27%. The linewidth of laser is less than 10 kHz, measured by the delayed self-heterodyne method with 10 km monomode fiber. SNR is about 56 dB. The lasing wavelength tuning is achieved by varying temperature of gratings. The lasing wavelength is tuned continuously over 1.02nm when its temperature is varied from 25°C to 90°C. That corresponds to a temperature sensitivity of 0.016nm/°C of these gratings. The output power in the tuning range is not flat because of the variation of gain in Erbium-doped fiber. The change of laser linewidth is less than 1 kHz with tuning. At the same time, no mode hopping is observed.7. Linewidth-narrowing mechanism in fiber laser by fiber saturable absorber has been analyzed theoretically. Single frequency Erbium-doped fiber ring laser is demonstrated by introducing fiber saturable absorber and passive fiber Bragg grating Fabry-Perot etalon in laser cavity. Frequency is stabilized by using short and low loss Erbium-doped fiber as saturable absorber. Stable single frequency 1550 nm laser is acquired. Lasing power is 39 mW, and the corresponding slope efficiency is 30%. SNR is larger than 50 dB. The linewidth is less than 10 kHz.更多还原