基于SPR原理的D型镀银光纤湿度传感器

Humidity Sensor of D-shaped Silver-coated Optical Fiber based on SPR Effect

【目的】为了获得更高灵敏度的光纤湿度传感器,文章提出了一种基于SPR原理的D型镀银(Ag)湿度传感器。【方法】文章将氧化石墨烯(GO)涂敷在D型镀Ag光纤表面,由于GO具有吸水特性且吸水后有效折射率(RI)会发生变化,当满足一定条件时会激发表面等离子体共振(SPR)效应,因此可以用作湿度传感。为了使传感器获得最大SPR灵敏度,首先通过COMSOL Multiphysics软件对D型镀Ag光纤的结构进行建模,采用有限元分析法探究抛磨深度和Ag膜厚度对传感特性的影响,然后通过实验验证结构参数的有效性和合理性,最后在D型镀Ag光纤表面再涂覆一层GO薄膜探究其湿度检测的性能。【结果】仿真结果表明,最佳传感器结构为抛磨深度为58.4μm、Ag膜厚度为50 nm,其在环境RI范围为1.34~1.40时获得的最大波长灵敏度为5500 nm/RIU。在该参数的基础上通过实验验证RI传感特性,传感器获得了最大为3668 nm/RIU的波长灵敏度,基准值R平方值为0.98,具有良好的线性。再在表面涂敷GO薄膜后,相对湿度由30%变化至90%,获得了0.545 nm/%RH的湿度灵敏度,相对湿度升高和降低两种情况下的线性R平方值分别为0.9611和0.9711,重合度良好。【结论】仿真结果和实际实验的共振峰变化区间相同,说明了该传感器的有效性和合理性,GO隔绝了Ag膜与空气的接触,防止了氧化,将其吸水特性和金属薄膜SPR特性结合所获得的光纤湿度传感器显示出了较高的灵敏度,为高灵敏度的湿度传感器设计提供了一种思路。

【Objective】In order to obtain a higher sensitivity fiber optic humidity sensor,this paper proposes a humidity sensor of D-shaped silver(Ag)-coated optical fiber based on Surface Plasmon Resonance(SPR)effect.【Methods】Graphene Oxide(GO)is coated on the surface of D-shaped Ag-coated optical fiber.Since GO has water absorption characteristics and the effective Refractive Index(RI)will change after absorbing water,SPR will be excited when certain conditions are met.Therefore,it can be used as a humidity sensor.In order to obtain the maximum SPR sensitivity of the sensor,the structure of D-type Ag-coated optical fiber is firstly modeled by COMSOL Multiphysics software,and the influence of polishing depth and Ag film thickness on the sensing characteristics is explored by finite element analysis.Then the structure is verified by experiments Validity and rationality of parameters.Finally,a layer of GO film is coated on the surface of the D-shaped Ag-coated optical fiber to explore its performance of humidity detection.【Results】The simulation results show that the optimal sensor structure is the polishing depth of 58.4μm,the thickness of the Ag film is 50 nm,and the maximum wavelength sensitivity of 5500 nm/RIU is obtained between the ambient RI of 1.34 and 1.40.On the basis of this parameter,the RI sensing characteristics are verified through experiments.The sensor has a maximum wavelength sensitivity of 3668 nm/RIU,and the R square value is 0.98,which has good linearity.After coating the GO film on the surface,the humidity sensitivity of 0.545 nm/%RH is obtained when the relative humidity changes from 30%to 90%,and the linear R-squared values under the two conditions of increasing and decreasing relative humidity are 0.9611 and 0.9711,respectively.【Conclusion】The simulation results and the actual experiment have the same resonance peak change range,which shows the effectiveness and rationality of the sensor.GO isolates the Ag film from contact with air,preventing oxidation.The optical fiber humidity sensor obtained by combining its water-absorbing properties with the SPR properties of the metal film demonstrates high sensitivity,providing a novel approach for the development of highly sensitive humidity sensors.