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利用双峰谐振效应,通过在长周期光纤光栅(LPFG)包层表面涂覆一层对周围气氛敏感的薄膜,建立了一种新型薄膜传感器,其双峰谐振波长间隔随薄膜折射率的变化而变化。基于三包层光纤光栅物理模型,根据耦合模理论研究了传感器的灵敏度Sn与薄膜光学参数(折射率n3和厚度h3)和光纤光栅结构参数(光栅周期Λ、折变量σ)之间的关系。采用最优化数值方法,确定了最佳的膜层光学参数和光栅结构参数。计算表明,该类型传感器对膜层折射率的测量分辨率高达10-7。
By using the bimodal resonance effect, a new type of thin film sensor was fabricated by coating a layer of LPFG on the surface of the LPFG. The bimodal resonance wavelength interval was dependent on the refractive index of the film Variety. The relationship between the sensitivity of the sensor Sn and the optical parameters (refractive index n3 and thickness h3) and the structure parameters (grating period Λ, fold change σ) of the fiber grating was studied based on the coupled-mode theory based on the physical model of the triple-clad fiber grating. Optimum numerical method was used to determine the optimal optical parameters and grating structure parameters. Calculations show that this type of sensor can measure the refractive index of the film up to 10-7.