The Integration Of Highly Sensitive Magnetic Measurement System Based On Ensemble Nitrogen-vacancy Centers And Its Application In Wireless Detection

The quantum state of microscopic particles in quantum magnetic sensing is extremely sensitive to external magnetic disturbance,and the limit sensitivity can reach a T magnitude,far exceeding the existing magnetic field detection methods.The magnetic field measurement based on Nitrogen-Vacancy（NV）centers in diamond has become a popular research direction for the new generation of magnetometers because of its high spatial resolution,no heating,measurement at room temperature and high sensitivity.The sensitivity of NV magnetometer has been reported to be beyond p T/（Hz）^1/2,however,the related research is based on large optical platform system.As the NV magnetometer is gradually oriented to engineering applications,the bulky,large NV magnetometer system that cannot be portable and mobile can no longer meet the corresponding needs.Therefore,in this paper,we focus on the research of highly sensitive integrated NV centers magnetometer,analyze the noise sources of NV magnetometer system,propose noise suppression methods for shot noise limited sensitivity,laser noise and electronics noise,and design and develop an integrated NV magnetometer prototype based on the optimized magnetic measurement method to achieve highly sensitive magnetic field measurement.On this basis,for the NV magnetometer array required for distributed sensing,the method of wireless microwave excitation diamond NV centers is proposed and combined with the principle of NV demodulation,the wireless detection of target information is realized.The main research contents of this paper are as follows:1.To address the problem of low sensitivity of the integrated NV magnetometer based on the modulation demodulation magnetometry method,the noise sources of the NV magnetometer system are analyzed,and the corresponding suppression methods are proposed for the main noises.In order to optimize the line width and photon detection rate in the limit sensitivity of the scattering noise,a finite element scan-like method is proposed to characterize the NV centers uniformity of the system,which provides a new technical means to select highly uniform diamond samples,and the high uniform NV centers distribution matched with uniform microwave excitation can effectively avoid the spreading of the resonance signal.Immediately afterwards,the fluorescence omnidirectional collection technology to achieve efficient collection of NV fluorescence,the collection efficiency increased from 33%to 65%,which in turn achieved the photon shot noise limited sensitivity improvement.For the electronics noise suppression,the microwave frequency modulation parameters optimization study was carried out,and the optimal modulation frequency bias and modulation frequency were obtained by combining simulation and experiment.Finally,the common mode noise suppression technology is combined to reduce the laser amplitude noise,which completes the suppression of several key noises in the magnetometer system and provides a theoretical and experimental basis for improving the sensitivity of the integrated NV magnetometer.2.In view of the problem that the bulky and portable large NV magnetometer system can no longer meet the requirements of engineering application,this paper carried out the design and integration of the head and system of NV magnetometer.In the early stage of the research,the miniaturization of the first-generation NV magnetometer head was realized through the high-precision micro-assembly and integration of fiber laser and diamond.The volume of the prototype is about 10 cm³.The high reflectivity prism fluorescence oriented collection method was used in the head to efficiently collect NV fluorescence,and the magnetic measurement sensitivity of the system was about 67 n T/（Hz）^1/2.On this basis,the sensor head was upgraded by using the fluorescence omnidirectional collection technology and laser common mode noise rejection technology,and the integration of the whole magnetometer control system was completed,and the sensitivity of the integrated NV magnetometer was measured to be 892.7p T/（Hz）^1/2@10Hz,and the shot noise limited sensitivity was calculated to be 325.8 p T/（Hz）^1/2,which is nearly one order of magnitude higher than the sensitivity index of the first generation miniaturized magnetometer prototype.This work provides a useful experience for the development of highly sensitive integrated NV magnetometers.3.In response to the need for multiple microwave generation modules in NV magnetometer arrays,a method of using wireless microwave excitation of diamond NV centers was proposed to achieve simultaneous excitation detection of multi-channel magnetometers.Based on this wireless transmission system combined with the principle of NV demodulation to achieve wireless detection of target information,the advantages of wireless microwave excitation of NV centers are further expanded and its possibilities in high frequency electromagnetic field detection are explored,with potential future applications in defense soldier health monitoring,wireless communication,radar detection,etc.