Koutsides C, Kalli K, Webb D J, Zhang L
Nanophotonics Research Laboratory, Cyprus University of Technology, Lemessos, Cyprus.
Opt Express. 2011 Jan 3;19(1):342-52. doi: 10.1364/OE.19.000342.
We present numerical modeling based on a combination of the Bidirectional Beam Propagation Method and Finite Element Method that completely describes the wavelength spectra of point by point femtosecond laser inscribed fiber Bragg gratings, showing excellent agreement with experiment. We have investigated the dependence of different spectral parameters such as insertion loss, all dominant cladding and ghost modes and their shape relative to the position of the fiber Bragg grating in the core of the fiber. Our model is validated by comparing model predictions with experimental data and allows for predictive modeling of the gratings. We expand our analysis to more complicated structures, where we introduce symmetry breaking; this highlights the importance of centered gratings and how maintaining symmetry contributes to the overall spectral quality of the inscribed Bragg gratings. Finally, the numerical modeling is applied to superstructure gratings and a comparison with experimental results reveals a capability for dealing with complex grating structures that can be designed with particular wavelength characteristics.
我们提出了一种基于双向光束传播法和有限元法相结合的数值模型，该模型能够完整描述逐点飞秒激光写入光纤布拉格光栅的波长光谱，与实验结果显示出极佳的一致性。我们研究了不同光谱参数的依赖性，如插入损耗、所有主要包层模和鬼模及其相对于光纤布拉格光栅在光纤纤芯中位置的形状。通过将模型预测结果与实验数据进行比较，验证了我们的模型，并实现了对光栅的预测建模。我们将分析扩展到更复杂的结构，其中引入了对称性破缺；这突出了中心光栅的重要性，以及保持对称性如何有助于提高写入布拉格光栅的整体光谱质量。最后，将数值模型应用于超结构光栅，与实验结果的比较表明该模型有能力处理可设计具有特定波长特性的复杂光栅结构。
