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掺Tm3+光纤激光器在工业、医疗、科技及军事领域具有重要应用前景。光纤布拉格光栅(FBG)是构成光纤激光器的重要元件。但掺Tm3+光纤不具备光敏性,利用紫外脉冲激光很难在其中刻写FBG,即使采用增敏技术提高其光敏性,获得的FBG的折射率调制量也很小,尚不能满足应用要求,阻碍了掺Tm3+光纤激光器全光纤化的发展。以相位掩模法的基本原理为基础,从理论上分析了以飞秒激光为刻写光源的技术要点,总结出与传统紫外激光刻写技术之间的差异及需要注意的问题。建立了飞秒激光相位掩模法刻写光纤光栅的实验系统,利用飞秒激光相位掩模法在非光敏光纤上刻写Bragg光栅,在非光敏掺Tm3+硅基光纤上获得了衍射阶次为二的光纤Bragg光栅,并给出了显微镜下观察到的光栅结构。实验结果证明:飞秒激光可以将FBG刻写入非光敏性硅基光纤,并且具有成栅时间短的优点。
Tm3 + doped fiber laser in the industrial, medical, technological and military applications have important prospects. Fiber Bragg Gratings (FBGs) are important components of fiber lasers. But doped Tm3 + optical fiber is not photosensitive, it is difficult to write FBG by UV pulsed laser, even if the sensitization technology is used to increase its photosensitivity, the refractive index modulation of FBG obtained is also very small, which can not meet the application requirements and hinder the Development of Tm3 + Fiber Laser All - Fiber. Based on the basic principle of the phase mask method, the technical points of using the femtosecond laser as a writing light source are theoretically analyzed, and the differences between the conventional UV laser writing technology and the problems needing attention are summarized. The experimental system for writing FBG with femtosecond laser phase mask was established. Bragg grating was written on non-photosensitive fiber by femtosecond laser phase mask method. The diffraction order was obtained on non-photosensitive Tm3 + Fiber Bragg grating, and gives the grating structure observed under the microscope. The experimental results show that femtosecond laser can write FBG into non-photosensitive silicon-based fiber and has the advantage of short gate-to-gate time.