表面镀层长周期光纤光栅双峰谐振及其透射谱研究

Dual-Peak Resonance and Transmission Spectrum in Coated Long-Period Fiber Grating

采用严格的耦合模理论,通过求解表面镀层长周期光纤光栅的特征方程,给出了双峰谐振波长的确定方法,以及它与光栅周期和模式序数之间的关系。结果表明,对应于较高次的包层模式,存在双峰谐振现象,且包层模式序数越高,与芯模产生谐振耦合所需的光栅周期越小。进一步讨论了双峰谐振波长的间距随薄膜参量与光栅参量变化的关系,描绘了这些参量对透射谱衰减谐振峰的影响,理论分析结果与X.W.Shu的无镀层长周期光纤光栅实验结果一致。这些研究为建立高灵敏的双峰谐振薄膜传感器提供了结构优化的理论支持。

By resolving the characteristic equation of coated long-period fiber grating （LPFG）, the dual peak resonant wavelengths is determined based on rigorous coupled-mode theory. The relationship between the dual-peak resonant wavelengths and grating period, the mode order is studied. The results show that the dual resonance appears in higher cladding mode, The higher the cladding mode order is, the smaller the related grating period required to couple with core mode is. Furthermore, the influence of film optical parameters and grating structure parameters on the intervals of dual-peak resonant wavelengths, as well as the attenuation peak of transmission spectra, are analyzed. The results are coincident with the non-coated long-period fiber grating experiment made by X. W. Shu. The research provides theoretical foundation for the structural optimization of dual-peak resonance film sensors with high sensitivity.