基于石墨烯膜的光纤Fabry-Perot腔干涉特性分析

针对以新型材料石墨烯为膜片的光纤法珀压力传感器,应用圆薄膜大挠度弹性理论,利用有限元法分析了均布载荷下石墨烯膜的挠度形变;并基于Fabry-Perot干涉仪原理,建立了光纤Fabry-Perot腔压力传感的数学模型.根据石墨烯膜折射率特性,分析了层数、入射光角度等参数对石墨烯膜反射率的影响,获取了腔长损耗以及薄膜挠度形变导致腔长变化而引起的干涉光谱变化规律.仿真结果表明,增加薄膜层数可提高反射率、改善干涉性能;但随着载荷增加,其对挠度形变的影响表现为反向递减效应.8层石墨烯薄膜可获得0.715%的反射率,且当腔长为40μm时,直径25μm薄膜的理论压力灵敏度约为10 nm/k Pa.这为基于多层石墨烯的膜片式光纤压力传感器的设计提供了理论依据.

Interference characteristics analysis of optical fiber Fabry-Perot cavity with graphene diaphragm

With regard to the design of optical fiber Fabry-Perot cavity using graphene as sensitive diaphragm, the deflection change under uniformly distributed loads in graphene film was analyzed by finite element method based on the large deflection elastic theory of circular film. The pressure-sensing mathematical model of optical fiber Fabry-Perot cavity with graphene diaphragm was established based on the working principle of Fabry-Perot interferometer. The effects of graphene film layer and incident light angle on the film reflectivity were obtained according to the refractive index characteristics of the film. Then the interference spectra change, caused by both the cavity length losses and the film deflection deformations under the pressure loads, were analyzed. The simulation results show that adding the film layer can increase the film reflectivity and further improve the optical interference performance; however, a decreasing effect on the deflection deformation is caused by the film layer with the increase of pressure load. Thus, an 8 layer graphene film can achieve a reflectivity of 0.715% and an approximate theoretical sensitivity of 10nm/kPa for a 40μm Fabry-Perot cavity length with a membrane diameter of 25μm. It provides a theoretical basis for the design and fabrication of high-sensitivity fiber-tip pressure sensor with multiple-layer graphene diaphragm.