三包层长周期光纤光栅谐振波长与薄膜光学参数的关系

The relation between resonant wavelengths and film optical parameters of triple-clad long-period fiber grating

通过求解严格的耦合模理论建立的三包层结构长周期光纤光栅特征方程,研究了三包层长周期光纤光栅谐振波长与第二包层(薄膜)的折射率和厚度之间的关系。结果发现,随着膜厚及折射率的增大,谐振波长偏移的变化分成三个区域,这与Nicholas D R的实验结果相符。利用HE/EH模的判据数,对三个区域的模特性进行了分析,给出了区域划分的衡量标准。给出了在不同薄膜参数时的长周期光纤光栅透射谱,发现一阶低次HE模式的耦合强度要远大于一阶低次EH模式。

By resolving the eigenvalue equation of triple-clad long-period fiber grating based on rigorous coupled mode theory, the relationship between the resonant wavelengths of triple-clad long-period fiber grating and the thickness as well as the refractive index of the second cladding（thin film） was studied. The results show that the shift of resonant wavelengths can be divided into three regions, which agrees with the experiment result of Nicholas D R. The mode characteristic of the three regions was analyzed using the criterion coefficient of HE/EH mode, and the standard of region division was given. The transmission spectrum of triple-clad long-period fiber grating of different film parameters is given, and it is found that the coupling strength of low-order ι = 1 HE modes is stronger than that of low-order ι = 1 EH modes.