掺镱光纤光子暗化效应研究

【作者】 刘波；

【导师】 侯超奇； 王勇刚；

【作者基本信息】 陕西师范大学 ， 工程硕士（专业学位）， 2020， 硕士

【摘要】 随着掺Yb光纤激光器的迅速发展,光子暗化效应成为制约其功率提升的重要因素之一,为了解决这一难题,围绕掺Yb光纤光子暗化效应,以其组分、光子暗化效应机理为基础,通过优化基质组分、掺杂不同浓度的Ce₂O₃,采用改进型化学气相沉积法结合螯合物气相沉积技术制备掺Yb铝磷硅三元体系光纤和Yb/Ce共掺铝硅二元体系光纤,测试光子暗化效应附加损耗,分析P₂O₅、Ce₂O₃抑制光子暗化效应的微观机理,为高功率光纤激光器抑制光子暗化效应提供理论基础。论文的主要内容包括:（1）基于改进型化学气相沉积法结合螯合物气相沉积技术,介绍了掺Yb有源光纤预制棒的制备工艺、光纤拉丝工艺。通过测试光纤预制棒的元素分布、折射率分布、荧光性能、吸收系数以及光纤纤芯损耗,分析预制棒的光学性能。熔缩工艺中部分P₂O₅、SiF₄挥发和部分离子迁移导致预制棒芯部中心组分含量分布较少,引起折射率分布不均匀。同时,掺杂P₂O₅影响掺Yb光纤的发光性能和光纤纤芯背景损耗。（2）通过976nm半导体激光诱导掺Yb铝磷硅三元体系光纤发生光子暗化效应,系统的研究了不同P₂O₅和Al₂O₃的掺杂浓度比例对光子暗化效应的影响,根据拉伸函数拟合光子暗化效应附加损耗随时间的变化关系。实验结果表明,当P/Al比例为1.18时,平衡态附加损耗仅为1.05dB/m,光子暗化速率为4130min。研究发现短光纤、高功率泵浦光导致掺Yb铝磷硅三元体系光纤的粒子数反转水平高,增加了平衡态附加损耗,加快光子暗化速率。Yb/Ce铝硅二元体系光纤光子暗化效应附加损耗实验表明,当Ce₂O₃与Yb₂O₃的掺杂浓度比例为0.62时,光子暗化效应性能最强,平衡态附加损耗达到7.53dB/m,但光子暗化速率达到42min。（3）根据协同光谱和激光拉曼光谱,掺Yb铝磷硅三元体系光纤中的Al₂O₃与P₂O₅能够抑制Yb³⁺团簇效应,降低能量上转换发生的概率,减少短波长光子诱导形成光子暗化色心的数量,从而实现抑制光子暗化效应的目的,但过量的P₂O₅能够生成新的缺陷,降低光子暗化效应性能。Yb/Ce共掺铝硅二元体系光纤中,Ce³⁺通过捕获空穴抑制AlOHC的形成,Ce³⁺⁺捕获电子抑制Yb³⁺价态变化,在一定程度上能够抑制光子暗化效应。两种体系的掺Yb光纤抑制光子暗化效应的实质是通过共掺组分降低光子暗化色心的数量,所以通过进一步优化掺Yb光纤纤芯组分条件,可以制备性能优越的高功率激光光纤,这为国内高功率激光器的发展提供了理论和实验基础。更多还原

【Abstract】 With the rapid development of Yb-doped fiber lasers,photodarkening has become one of the important factors restricting the increase of its power.In order to solve this problem,based on the photodarkening effect of Yb-doped fiber,based on its composition and photodarkening mechanism,by optimizing the matrix composition and doping Ce₂O₃ with different concentrations,Yb-doped aluminum-phosphorous-silicon ternary system optical fiber and Yb/Ce co-doped aluminum-silicon binary system optical fiber were prepared by using an modified chemical vapor deposition combined with chelate gas phase deposition.By testing the excess loss of photon darkening effect,the microscopic mechanism of P₂O₅ restricting photodarkening effect is analyzed,which provides a theoretical basis for high power fiber lasers to suppress photodarkening.The main content of the thesis includes:（1）Based on the modified chemical vapor deposition combined with chelate gas phase deposition technology,the preparation process of Yb-doped active optical fiber preform and fiber drawing process are introduced.The optical properties of the preform are analyzed by testing the element distribution,refractive index distribution,fluorescence performance,absorption coefficient,and fiber core loss of the optical fiber preform.The partial P₂O₅ and SiF₄ volatilization and partial ion migration in the melting and shrinking process lead to less distribution of the central component content of the preform core,resulting in uneven of refractive index distribution.Simultaneously,doping P₂O₅ affects the luminous performance of Yb-doped fiber and the background loss of fiber core.（2）The photodarkening effect of Yb-doped aluminum-phosphorous-silicon ternary fiber was induced by 976nm semiconductor laser.The affect of different P₂O₅ and Al₂O₃ doping concentration ratio on photodarkening was systematically studied.According to the stretching function,the relationship between the excess loss of photodarkening and time is fitted.The experimental results show that when the P/Al ratio is 1.18,the excess loss in equilibrium state is only 1.05dB/m,and the photodarkening rate is 4130min.The study found that short fiber and high-power pump light led to a high level of particle reversal of Yb-doped aluminum-phosphorus-silicon ternary fiber,which increased the excess loss of equilibrium state and accelerated the rate of photodarkening.Yb/Ce aluminum-silicon binary system optical fiber photodarkening excess loss experiment shows that when the ratio of the doping concentration of Ce₂O₃ and Yb₂O₃ is 0.62,it’s anti-photodarkening ability is the strongest,and the excess loss in equilibrium reaches 7.53dB/m,but the photodarkening rate reached 42 min.（3）According to the cooperative luminescence spectrum and laser Raman spectrum,Al₂O₃ and P₂O₅ Yb-doped aluminum-phosphorus-silicon ternary system fiber can suppress the Yb³⁺ cluster effect.The probability of energy up-conversion is reduced,and the number of short-wavelength photons induced to form a darkening color center is reduced,thereby achieving the purpose of suppressing the darkening effect of the photon.However,excessive P₂O₅ can generate new defects and reduce photodarkening performance.In the Yb/Ce co-doped aluminum-silicon binary system fiber,Ce³⁺ suppresses the formation of AlOHC by trapping holes,and Ce³⁺⁺ traps electrons to suppress the Yb³⁺ valence state change,which can overcome the photodarkening effect to a certain extent.The essence of Yb-doped fiber in two systems to suppress photodarkening is to reduce the number of photodarkening color centers by co-doping ions,so by further optimizing the Yb-doped fiber core component conditions,highperformance laser fibers with excellent performance can be prepared.This provides a theoretical and experimental basis for the development of domestic high-power lasers.更多还原