Research On Vector Magnetic Sensing Based On PDMS Flexible Resonator

Sensors are an important part of modern information technology and are widely used in technical fields such as aerospace,military industry,geological survey,and ocean exploration.High-sensitivity and high-resolution magnetic sensors are an important part of the information technology industry.In recent years,based on the whispering gallery mode（WGM）resonant cavity has a high quality factor,compact mode volume and other characteristics,making it a high-quality platform for optical sensors.In this paper,the research on the whispering gallery mode magnetic sensor is carried out on the platform of polydimethylsiloxane（PDMS）flexible resonant cavity optical element.The PDMS flexible resonant cavity and Nd Fe B magnet form a sandwich structure,the Young’s modulus of PDMS material is small and the corresponding deformation variation is larger than other materials,and the Nd Fe B magnet sandwich provides the function of magnetic field sensing,which has the advantages of high sensitivity and small size.In this paper,we make full use of these advantages to investigate the vector magnetic field sensing of this sandwich structure.The main work accomplished in this paper is as follows:（1）The development status of three kinds of optical resonant cavities and WGM resonant cavities is mainly described,and the development status of magnetic sensors based on whispering gallery mode resonant cavities is analyzed and outlined.Taking the PDMS flexible resonant cavity as the sensitive element,the electromagnetic field distribution in the PDMS flexible resonant cavity is discussed,the electromagnetic coil model is established,and the force on the magnet sandwich is analyzed by simplifying the magnetic field distribution of the electromagnetic coil under the magnetic field of the electromagnetic coil.The analysis is based on the magnetic field sensing principle of the flexible resonant cavity sandwich structure,the magnetic field distribution under different magnet spacing is simulated by finite element,the inherent properties of the material are consulted,and the amount of radius change of the PDMS flexible resonant cavity is simulated and calculated,and the maximum theoretical sensitivity is 3.79 nm/m T.Then the main characterization parameters of the PDMS flexible resonant cavity are introduced.（2）Proposed to prepare superhydrophobic coating on the slide,use the injector to control the morphology of PDMS flexible resonant cavity,use 8 mm diameter Nd Fe B magnet and PDMS flexible resonant cavity to form a magnetic sensitive unit-sandwich structure,and three PDMS flexible resonant cavities to provide the stability of the sandwich structure,and realize the sandwich structure by increasing the number of slides variables.The shelf for tapered fiber encapsulation was designed,and the preparation of tapered fibers with tapered area diameter range from 1μm to 3μm was performed by a molten fiber pulling taper machine.The tapered fiber with a tapered region diameter of 2.1μm is used in the experiment,and the effective refractive index simulation of the tapered region is completed by simulation,and the simulation results are similar to the PDMS refractive index,so the mode matching can be completed.The main characterization parameters of the PDMS flexible resonant cavity were measured,and the Q value of the PDMS flexible resonant cavity was measured to be1.41×10⁵.（3）The vector magnetic field sensing model of PDMS flexible resonant cavity is studied,and the influence of the quality factor of PDMS flexible resonant cavity in sandwich structure with different spacing is analyzed by designing and building the experimental system of magnetic field sensing,and the magnetic field calibration of the energized coil is performed,and the red and blue shift sensitivity of magnetic field sensing of sandwich structure is tested,and the maximum red shift sensitivity is 1.08 nm/m T,and the maximum blue shift The maximum redshift sensitivity was 1.08 nm/m T and the maximum blueshift sensitivity was1.12 nm/m T.The reasons for the difference in redshift and blueshift sensitivity were analyzed,and the theoretical sensitivity was compared with the experimental sensitivity to analyze the reasons for the difference.The PDH frequency stabilization technique is introduced to detect the frequency response curve of magnetic sensing by rotating the coil to detect the vectoriality of the sandwich structure with a notch depth of 34.6 d B using PID frequency locking.The minimum detection limit of this magnetic field sensor is 0.96 n T/Hz^1/2by detecting the frequency response curve in the Hz to k Hz range.