【摘 要】
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石英光纤作为常见的一种传能光纤,在高能激光照射条件下易产生损伤,从而影响整个光学系统的传输效率。在造成激光诱导光纤损伤的机理中,光纤热效应造成的损伤极易对光纤系统造成影响。目前,使用有限元法对石英光纤热效应和损伤性质的研究较少,本文通过使用有限元方法,在高纯石英光纤模型中研究了千瓦级激光引起的热损伤。通过模拟计算研究了光纤损耗,热吸收和熔融损伤。利用有限元方法,在高纯石英光纤模型中研究了高能激光引
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石英光纤作为常见的一种传能光纤,在高能激光照射条件下易产生损伤,从而影响整个光学系统的传输效率。在造成激光诱导光纤损伤的机理中,光纤热效应造成的损伤极易对光纤系统造成影响。目前,使用有限元法对石英光纤热效应和损伤性质的研究较少,本文通过使用有限元方法,在高纯石英光纤模型中研究了千瓦级激光引起的热损伤。通过模拟计算研究了光纤损耗,热吸收和熔融损伤。利用有限元方法,在高纯石英光纤模型中研究了高能激光引起的热损伤。使用波动光学,射线光学,固体加热,波束包络法等方法,对千瓦级激光入射石英光纤内部产生的热效应进行了模拟。通过模拟计算分析了光纤表面温度随时间变化情况与内部热场分布。本论文的主要研究内容如下:（1）激光入射光纤的有限元模型构建。对使用短焦透镜聚焦激光入射进入光纤的耦合结构进行了还原,使用波长为1064 nm的千瓦级激光作为入射光源,通过光线追迹得到入射光源的焦斑半径;（2）高能激光对光纤表面作用的热分析。通过波动光学方法计算出激光入射进光纤内所产生的损耗,等效为石英光纤输入端热源功率,通过固体加热方法仿真得到石英光纤表面温度、内部温度分布,及表面最高温度随时间变化情况。（3）热场分布对光纤非线性效应的影响。采取波束包络法,对比分析了热场存在对石英光纤非线性效应的影响。计算得到石英光纤内部电场模与折射率分布,进而得出石英光纤传能效率降低的结果。比较和分析了有无热场分布下高纯石英光纤的折射率变化。结果表明,如果没有适当的热管理,超过1000W的1064 nm激光注入将对高纯度石英光纤的表面造成熔融损伤,热场分布的存在会加重石英光纤的非线性效应,影响传能效率。该研究对于与激光引起的光纤损伤相关的研究具有的理论指导作用。
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