大功率光纤激光系统光谱特性研究

发布时间：2018-12-25 18:42

【摘要】：光谱特性是光纤激光的基本物理特性之一。随着光纤激光系统输出功率的提高,非线性效应对系统的影响越来越显著:一方面,在光纤激光系统中,光谱特性是系统中非线性效应及破坏效应的直观表征;另一方面,光纤激光的光谱特性也会对光纤器件及系统的稳定性产生影响。基于此,本文对高功率光纤激光系统的光谱特性展开了理论与实验研究。论文回顾了国内外有关光纤激光系统光谱特性的研究进展,分别介绍了掺镱光纤激光器、拉曼光纤激光器及掺镱光纤放大器的典型光谱特性模型,并总结了相关模型优点及不足。通过对速率方程及非线性传输方程的分析,建立了多纵模振荡器及超荧光光源的光谱特性模型,并分析了光纤光源参数对其输出光谱特性的影响。研究结果表明,对多纵模振荡器而言,其输出光谱宽度随高反射率光栅的反射谱宽、泵浦功率及腔长的增长是近似线性展宽的,而输出光栅的反射谱宽对输出光谱的影响可以忽略;对超荧光光源而言,随着掺杂光纤长度的增加,其输出光谱的中心波长逐渐向长波方向漂移。通过种子源特性及放大过程的描述,对光纤放大器的光谱演化过程进行分析,建立了高功率光纤放大器的光谱特性数值仿真模型,并研究了种子源特性及放大器的参数对输出光谱特性的影响;同时采用不同种子源进行了相应的实验验证,实验结果与理论仿真结果较好吻合。最后,推导了不同输出功率下光纤放大器的光谱展宽因子的近似表达式。建立了包含受激拉曼散射效应的光纤激光器动力学方程,并研究了种子源特性及光谱滤波对其在放大过程中拉曼阈值特性的影响。数值仿真计算结果表明,种子源的时域特性会对光纤放大器的拉曼阈值特性产生显著影响。
[Abstract]:Spectral characteristic is one of the basic physical properties of fiber laser. With the increase of the output power of the fiber laser system, the nonlinear effect becomes more and more obvious. On the one hand, in the optical fiber laser system, the spectral characteristic is the direct representation of the nonlinear effect and the destruction effect in the optical fiber laser system. On the other hand, the spectral characteristics of fiber laser also affect the stability of optical fiber devices and systems. Based on this, the spectral characteristics of high power fiber laser system are studied theoretically and experimentally. This paper reviews the research progress of optical fiber laser system at home and abroad, and introduces the typical spectral characteristic models of ytterbium-doped fiber laser, Raman fiber laser and ytterbium-doped fiber amplifier, respectively. The advantages and disadvantages of the models are summarized. Based on the analysis of the rate equation and the nonlinear transmission equation, the spectral characteristic models of the multi-longitudinal-mode oscillator and the superfluorescence source are established, and the influence of the optical fiber source parameters on the output spectral characteristics is analyzed. The results show that the output spectral width increases linearly with the reflection spectrum width, pump power and cavity length of the high reflectivity grating for the multi-longitudinal mode oscillator. The effect of the reflectance spectrum width of the output grating on the output spectrum can be neglected. For the superfluorescent light source, the central wavelength of the output spectrum drifts to the direction of long wave with the increase of the length of doped fiber. Based on the description of seed source characteristics and amplification process, the spectral evolution process of fiber amplifier is analyzed, and a numerical simulation model of spectral characteristics of high power fiber amplifier is established. The effects of the characteristics of the seed source and the parameters of the amplifier on the output spectral characteristics are also studied. At the same time, different seed sources were used to verify the results, and the experimental results were in good agreement with the theoretical simulation results. At last, the approximate expression of spectrum broadening factor of fiber amplifier with different output power is derived. The dynamic equation of fiber laser with stimulated Raman scattering effect is established. The effects of seed source characteristics and spectral filtering on Raman threshold characteristics during amplification are studied. The numerical simulation results show that the time domain characteristics of the seed source have a significant effect on the Raman threshold characteristics of the fiber amplifier.
【学位授予单位】：国防科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN24

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