Study On High Sensitive Optical Waveguide Magnetic Field Sensor Based On Magnetic Fluid

The continuous development of emerging technologies has brought more efficient and convenient life to today's society,so the demand for information is also enhanced.As an important tool for sensing information and transmitting information,sensors have attracted the attention of domestic and foreign scientists and are also one of the important directions of scientific research.According to the sensing physical quantity,the sensors can be divided into temperature sensor,humidity sensor,gravity sensor,flow sensor,electric field sensor,magnetic field sensor and so on.Among them,magnetic field sensing has a wide range of needs in many fields such as people's life and work;and hence,an important research value.Early magnetic field sensors were mainly divided into induction coil sensors,fluxgate sensors,magnetoresistive sensors,Hall sensors,etc.However,with the rapid development of science and technology,our requirements for sensing are getting higher and higher,and the early magnetic field sensors gradually shows a series of shortcomings such as complex structure,high cost,poor adaptability and small dynamic range.In recent years,magnetic fluid magnetic field sensors based on magnetic fluids have received considerable attention due to their advantages of strong adaptability and small size.However,the structure of the fiber-optic magnetic field sensor is relatively simple,and is mainly divided into three structures: a grating,an F-P cavity,and a fusion taper.Compared with optical fibers,optical waveguides have many advantages such as different waveguide materials,flexible structure,simple processing technology,low price,and easy to integrate.In view of this,this dissertation proposes a magnetic field sensor that combines a magnetic fluid with a Mach-Zehnder interferometer(MZI).The MZI interferometer has a simple structure,and it is expected to realize high-sensitivity magnetic field sensing by introducing a magnetic fluid as a cladding in one arm of the interferometer.The master revolves around the design,fabrication and testing of sensors to verify the effect of magnetic field sensing.The main research contents are as follows:(1)The development history of optical sensors and magnetic field sensors is introduced,and we also analyze the advantages and disadvantages of magnetic fluid-based magnetic field sensors based on different structures,and explain the research objectives and significance of the master.Then we describe the basic properties and applications of magnetic fluids briefly.(2)We select the waveguide material according to the experimental conditions,and use the dispersion equation of the rectangular waveguide and the MATLAB software to simulate the dispersion curve to determine the waveguide size.The coupling mode theory and Rsoft software are used to simulate the two-port energy output of the directional coupler to determine the coupling pitch and coupling length.Finally,the length of the sensing arm is determined to complete the design of the entire device.(3)The optical waveguide magnetic field sensor is fabricated by sputtering,exposure,development,etching,etc,and the device is packaged by ultraviolet glue.(4)An experimental test system is set up to test the near-field spot,liquid refractive index sensitivity and magnetic field sensing sensitivity of the magnetic field sensor in turn.The maximum liquid refractive index sensitivity of the test was 6384 nm/RIU,and the maximum magnetic field sensitivity was22.6 pm/Gs.