Research Of Vector Magnetic Field Measurement Method And Application Based On NV Color Centers In Diamond

Magnetic field measurement is widely used in military defense,biomedicine,resource exploration,space exploration and molecular exploration and plays an important role.With the development of science and technology and the increasing demand for magnetic measurement and the diversification of applications,it faces the demand of higher sensitivity and higher resolution.In recent years,the development and progress of quantum technology has promoted the innovation of communication,computing,navigation and other technologies,giving the possibility of breakthrough the limit of diversified physical quantity sensing measurement.The nitrogen-vacancy（NV）color center,as an emerging quantum spin solid state sensing structure,because of the advantages of long spin coherence time at room temperature,coherent microwave spin manipulation,optical spin state initialization and readout,and good biological compatibility and so on,has been extensive research and applied to many frontier fields in high sensitivity(p T/Hz^1/2),high resolution（sub-nm）,small sensitive volume and high signal-to-noise ratio,etc.NV color center quantum sensing provides a brand new means for high precision magnetic measurement technology and has great potential in hhigher magnetic sensitivity in the future.Based on this,the research of vector magnetic field measurement method and application based on NV color centers in diamond in this paper includes:1.Based on the NV color center magnetic sensitivity mechanism,the active detection technology of continuous microwave frequency modulation with high-precision multi-axis vector magnetic field closed-loop feedback is proposed,and the magnetic detection sensitivity is increased to 1.5 n T/Hz^1/2.The mechanism of the diamond NV color center sensitive magnetic field were studied based on Hamiltonian theory.A closed-loop feedback magnetic measurement and detection system with microwave frequency modulation is established.The NV color center excitation,fluorescence generation and signal collection are described in detail.A confocal optical path with electron spin excitation of NV color center,fluorescence collection,laser spot adjustment and variable power was built.In phase-locked frequency discrimination,the modulated fluorescence ODMR signal was derived by using optical Bloch method and the NV color center five-level system.The optimal modulation parameters were obtained by simulation（modulation frequency 16.5 k Hz,modulation amplitude 8 V,modulation phase 80^o,modulation depth 2.8 MHz）.At the same time,the closed-loop inverse active detection feed technology is adopted to improve the stability and anti-interference ability of the NV magnetic measurement,and realize the measurement of vector magnetic field by real-time tracking of multiple NV axes at the same time.2.Based on the magnetic field enhancement principle of magnetic flux concentrators（MFC）,the high precision magnetic field measuring combined with MFC and NV spin magnetic measurement system is developed,effectively improved the detection sensitivity to 0.13 n T/Hz^1/2.The principle of MFC is simulated and analyzed firstly,and the structure of T-shaped MFC is designed.Then the continuous wave optical probe magnetic resonance technique was used to verify the magnetic enhancement effect,and the enhancement factor was about 13times.By comparing the NV magnetometer with or without MFC,the sensitivity of magnetic measurement is improved from 1.5 n T/Hz^1/2to 0.13 n T/Hz^1/2.At the same time,the relationship between different spacing widths and magnetic enhancement multiples is explored and the NV magnetometer with adjustable range is realized.3.Based on the high sensitivity characteristic and the principle of axial angle sensitivity of the NV color center,the high sensitivity micro-angle measurement method is proposed.The micro-angle measurement is realized by dual-channel differential detection technology,and the test results results show that the sensitivity can reach 0.092mdeg/Hz^1/2(0.16 n T/Hz^1/2).Based on the Hamiltonian perturbation theory and axial angle sensitivity mechanism of the NV center,the theoretical analysis is carried out.A micro-angle measurement system is built for single-channel and dual-channel differential locking detection technology.The experiment result shows that the dual-channel differential system can effectively suppress the reciprocity noise and improve the measurement accuracy,and the micro-angle measurement sensitivity is 0.092 mdeg/Hz^1/2(0.16 n T/Hz^1/2).The research provides a certain technical basis for NV color center high precision magnetic measurement in the attitude angle measurement and spatial angle real-time tracking of micrometer and nanometer weak magnetic dynamic objects.