中文摘要：

理论分析了利用高频CO2激光脉冲在不同类型光纤中写入长周期光纤光栅（LPFG）时光纤包层和纤芯发生折射率改变的机理和计算方法.结果表明,残余应力释放、快速固化、光纤致密化和熔融变形是高频CO2激光能成栅的主要原因,但采用不同的写入方法、不同的激光写入能量在不同的光纤类型上制作光栅时各种机理的重要性不同.利用长周期光纤光栅对构成的M-Z干涉仪实验测量了高频CO2激光以不同辐射能量在光纤不同作用位置所引起的光纤纤芯或包层的折射率平均变化量,并通过实际制作光栅的过程来初步验证光纤折射率的变化情况.CO2激光与光纤相互作用机理的分析和实验研究为利用这种方法制作折变型全光纤器件提供了实验制作的基础和完善工艺的方法.

英文摘要：

The mechanism of refractive index change of long period fiber gratings （LPFGs） induced by high frequency CO2 laser pulses is investigated in theory and by experiment. It is found that the release of residual stress, rapid solidification, fiber densification and fusion distortion are discovered to be the main mechanisms of formation of this kind of gratings. The above four mechanisms play different roles when different fibers, different scanning methods and the different laser power were used in the process of LPFG fabrication. The average refractive index changes of the core and cladding were measured by using M-Z interferometer formed by LPFG pair in this paper, which provides the experimental basis for fabricating all-fiber devices.