基于光子晶体光纤交叉敏感分离的磁场温度传感研究

提出了一种基于定向耦合效应和表面等离子共振效应的交叉敏感分离的磁场温度传感结构.在光子晶体光纤的一个特定空气孔中填充磁流体,利用磁流体的磁光效应和定向耦合效应形成磁场传感通道;在垂直方向的另一空气孔的内壁镀金纳米薄膜并填充甲苯液体,利用甲苯的温敏效应和表面等离子共振效应形成温度传感通道.对应输出谱出现两个损耗峰,测量损耗峰位置可以间接测出磁场强度和温度变化.通过理论计算()和结构优化,在90—270 Oe1 Oe=10~3/(4π) A/m范围内,磁场强度的灵敏度最高可达1.16 nm/Oe;在25—60?C范围内,温度的灵敏度可达-9.07 nm/?C.虽然填充的两种液体的折射率都受环境温度的影响,但通过建立灵敏度系数矩阵,可以消除磁场强度与温度的交叉敏感,实现磁场温度双参量的高灵敏度检测.

Simultaneous measurement of magnetic field and temperature based on photonic crystal fiber with eliminating cross-sensitivity

Measurement of magnetic field is very important in many fields, such as industrial manufacture, marine environmental monitoring, medical testing, etc. However, there is a cross sensitivity between the measurement of magnetic field and the fluctuation temperature in the environment. So how to accurately measure the magnetic field and the temperature simultaneously by eliminating the cross-sensitivity has been an urgent problem. In recent years, photonic crystal fiber (PCF) sensor has been widely used due to its particular advantages, such as high sensitivity, small size and its flexibility of filling various sensitive media into the air hole. So the PCF provides a new idea for designing the high-sensitivity magnetic sensor. In this paper, a new PCF sensing structure based on the mixed effects of directional resonance coupling and surface plasmon resonance (SPR) is proposed. In the cladding of the PCF, one air hole infiltrated with the magnetic fluid (MF) forms a defect core and is used as a directional coupling channel. When the wave vector matching condition is satisfied in the directional coupling channel, the power is transferred from the fiber core region to the clad defect core at a particular wavelength, and a loss peak is generated in the transmission spectrum. The MF has its unique magneto-optical effect. This is because its refractive index changes with external magnetic field. So the loss peak can be shifted with the magnetic field at a fixed temperature. Another air hole coated with a gold nano film and infiltrated with the methylbenzene is used as the SPR channel. So plasmon modes are excited, and the resonance peak occurs when the real part of the effective index of the core mode is equal to that of the SPR mode at a particular wavelength. The resonance peak can also be shifted with the index of the methylbenzene at changed temperature. The simulation and numerical analysis of the magnetic field and temperature sensing characteristics of the structure are carried out, and the structure parameters of PCF are optimized by COMSOL Multiphysics through using the finite element method under the boundary condition of perfectly matched layer. In a magnetic field range of 90-270 Oe and in a temperature range of 25-60 ℃, the highest magnetic field sensitivity and temperature sensitivity are respectively 1.16 nm/Oe and -9.07 nm/℃, each with a good linearity in the sensing structure. To eliminate the cross sensitivity between the temperature and magnetic field, a sensitivity coefficient matrix is established. As a result, the highly sensitive double-parameter detection of magnetic field and temperature is realized. Moreover, this sensing structure can be used in an extensive range, which has a certain potential value and practical significance.