薄包层长周期光纤光栅薄膜传感器特性研究

Film Sensor Based on Long-Period Fiber Grating with Reduced Cladding

基于薄膜参量变化引起的长周期光纤光栅模式重组机制,系统研究了光纤包层半径变化对长周期光纤光栅薄膜传感器特性的影响.结果表明,在相同薄膜参量下包层半径的减小可有效提高传感器的灵敏度,并增大传感器对薄膜参量变化响应的动态范围,但减小包层半径对传感器的增敏效应随薄膜厚度的增大而减小.通过氢氟酸腐蚀减小包层半径,采用静电自组装法在包层表面镀制PAH/PAA薄膜,镀膜过程中光纤光栅输出的光谱数据证实了理论分析结果.实验结果表明:半径为39μm、膜厚为424nm的长周期光纤光栅薄膜传感器在溶液pH值检测中的灵敏度达3.93nm/pHU,比标准包层时的灵敏度提高了1倍.

Based on the mode-reorganization mechanism of long-period fiber grating induced by the increase of film thickness, the influence of cladding radius on the characteristics of long-period fiber grating-based film sensor was investigated. The results show that the reduction of fiber cladding can improve the sensitivity of film sensor in a great manner for given film parameters and enlarge the dynamic range of the response of film sensor to the variation of film thickness. Moreover, the sensitivity- increasing effect caused by cladding reduction is degraded by the increase of film thickness. In experiment, the cladding was reduced with hydrofluoric acid and the organic film of PAH/PAA was deposited by electrostatic self-assembly method. The theoretical results are confirmed by analyzing the spectral data during film deposition. The application of this film sensor in pH sensing shows the sensitivity reaches 3.93 nm/pHU when the cladding was 39（m and film thickness was 424 nm, which was two times as high as that of common fiber cladding.