镀金属两层膜系长周期光纤光栅模式转换与折射率响应  

Mode Transition and Refractive Index Response in Long-Period Fiber Grating Coated with Double-Layer Overlays Including Metal Film

作　　者：顾铮■ 蓝锦龙[1] 

机构地区：[1]上海理工大学理学院光电功能薄膜实验室,上海200093

出　　处：《光学学报》2014年第4期83-88,共6页Acta Optica Sinica

基　　金：国家自然科学基金(60777035);教育部科学技术研究重点项目(208040);上海市教育委员会科研创新重点项目(11ZZ131);上海市重点学科建设项目(S30502)

摘　　要：基于耦合模理论,研究了镀金属两层膜系长周期光纤光栅(LPFG)的模式转换及其折射率响应特性。从表面等离子体共振(SPR)的激励条件和模式转换发生条件出发,指出镀金属两层膜系LPFG中的SPR和模式转换不会同时发生,在此基础上分析了镀金属两层膜系LPFG包层模有效折射率随敏感薄膜厚度的变化,发现镀金属两层膜系LPFG的模式转换区域比镀膜LPFG的转换区域要宽,且模式转换区域内第一次转换时的有效折射率变化斜率比镀膜LPFG的大,意味着在该区域其对敏感膜层的变化有更高的响应。考察了金属薄膜厚度对镀金属两层膜系LPFG包层模有效折射率的影响,结果表明,随着金属薄膜厚度的增加,第一次转换时有效折射率的变化斜率逐渐增加。分析了第一次转换时镀金属两层膜系LPFG透射谱对敏感薄膜折射率变化的响应特性,结果表明,镀金属两层膜系LPFG传感器对敏感薄膜折射率的灵敏度明显高于镀膜LPFG,对敏感薄膜折射率的灵敏度的分辨率可达10-6。Based on the coupled-mode theory, the mode transition in long-period fiber grating （LPFG） coated with double-layer overlays including metal film and refractive response characteristics of overlay thickness have been studied. According to the excitation condition of surface plasmon resonance （SPR） and the occurrence condition of the mode transition, it is pointed out that its SPR and the mode transition do not occur at the same time, based on which, the changes of the efficient index of LPFG coated with double-layer overlays including metal film with sensing film thickness are analyzed, and it is obtained the mode transition zone of LPFG coated with double-layer overlays including metal film is wider than that of coated LPFG, and the slope of the efficient index of the first transition in the mode transition zone is bigger than that of coated LPFG, which means that there are higher responses for the variations of the sensing film thickness in this zone. The influences of metal film thickness on the refractive index of LPFG coated with double-layer overlays including metal film are further investigated. The result shows that the slope of efficient index increases gradually with the increase of the metal film thickness in the first transition of the first mode transition zone. The response characteristics of transmission spectrum of LPFG coated with double-layer overlays including metal film with sensing film refractive index in the first mode transition are investigated. The results indicate that sensitivity of sensing film refractive index of LPFG coated with double-layer overlays including metal film is higher than that of coated LPFG, and the resolution of the sensitivity of sensing film refractive index can be 10^-6.

关 键 词：光纤光学 镀膜长周期光纤光栅 模式转换 灵敏度 

分 类 号：TN253[电子电信—物理电子学]