Research On Magnetic Sensing Technology Based On Photonic Crystal Slab Microcavity

With the advent of the Internet of Things(IOT),as a key device for data collection and transmission,sensors will surely get rapid development and application in the future.Among them,magnetic sensor is an important component of the sensor,which is widely used in daily life and industry.At present,the development trend of magnetic sensor technology is high sensitivity,high stability,high anti-interference,miniaturization and integration.As a new type of optical microsensor,photonic crystal sensor not only has the advantages of optical sensor,but also has the characteristics of simple structure,small size,and easy integration,which meets the development requirements of sensor technology in the future.This paper proposes a new method for the photonic crystal slab microcavity applied magnetic field measurement,the main contents and innovations are as follows:Firstly,by researching and summarizing the current magnetic measurement methods and principles of Photonic Crystals,combined with the feasibility of practical applications,the magnetic sensing method based on the photonic crystal slab(PCS)microcavity was selected.In order to meet the design requirements of the sensor,we optimizes the structure of the photonic crystal and its microcavity,obtains a photonic crystal structure with a TM forbidden band width of up to 0.2342(?a/2?c),and makes the quality factor of the microcavity above 2.8×10~5.At the same time,the structure of the micro-cavity side-coupled straight waveguide is determined.Combined with the theory of photonic crystal evanescent field sensing,this paper constructed a PCS magnetic sensor structure model and analyzed its sensing mechanism in detail.Secondly,the Finite Difference Time Domain(FDTD)method is used to numerically simulate the structure of the PCS magnetic sensor.By analyzing the sensing characteristics,it is found that the new photonic crystal magnetic sensor has high linearity and sensitivity.Next,by studying the influence of various factors on the sensor sensitivity,including the thickness of the magnetic sensitive film,the type of emission field excitation,and the PCS method covered by the magnetic sensitive film,the research results show that:in TM mode,when the thickness of the magneto-sensitive film in the PCS magnetic sensor is L=0.4?m,the type of emission field excitation is continuous wave,and the magneto-sensitive film is completely covered on the PCS surface,the PCS magnetic sensor has the best sensitivity,and its sensitivity S can reach 2.52/T.Finally,in order to improve the sensitivity of the PCS magnetic sensor,the sensor structure has been optimized.By studying the sensing characteristics of the Y-type waveguide coupling with a single microcavity and the W1-type waveguide coupling with a multi-microcavity structure,it was found that the sensor sensitivity of the multi-microcavity coupled single-waveguide structure is low,while the sensor sensitivity S of the single-microcavity coupled Y-waveguide structure can be increased to 3.31/T.Through analysis,it can be concluded that increasing the number of transmitters,reducing light wave loss in photonic crystals,and improving the coupling efficiency of microcavity and waveguide can enhance the sensitivity of the sensor.