用相位掩模法制作光纤光栅的技术

准分子激光照射相位掩模后，在近场形成周期的条纹分布，利用近场光强对光敏光纤进行曝光，可以在纤芯中写人光栅。对光纤光栅折射率分布进行合理假设，运用耦合模理论计算了光纤光栅的反射率，对其反射率与相关参数的关系进行了讨论，并且分析了用相位掩模技术制造光纤光栅的影响因素，得出要获得窄带宽高反射率光栅需有适当的折射率调制和大的光纤光栅长度的结论。另外还导出了掩模板后表面的近场光强分布和光纤光栅的周期公式。

Fabricating technology of fiber grating with phase masks

When excimer laser irradiate phase masks, the periodic fringe patterns are formed in near field, exposing fiber to it, in core gratings can be induced. Using the coupled mode theory, we deduce the reflected power of the fibre grating with a reasonable assumption of the refraction index distribution. Relationships between the reflected power and relevant fibre parameters are discussed. And influence factors of fiber gratings fabricating are analysed. We gain the conclusions that the suitable refraction index modulation and long grating length are needed for making the narrow bandwidth and high reflected power fiber gratings. The near field intense distribution of the phase mask back surface and period formulas of fiber gratings are obtained.