Research Of Optical And Magnetic Response Properties And Preliminary Implementation Of The Cesium Magnetometer

Precision measurement has always been the frontier of scientific research.As a branch of precision measurement,magnetic field measurement has been widely applied ranging form biomedicine,magnetic anomaly detection,inertial navigation,space exploration,to the research of basic physics.Compared with other types of magnetometers,atomic magnetometers have obvious advantages in many aspects.For example,they can achieve extremely high sensitivity with non-cryogenic operation,which makes the application prospect of atomic magnetometers more extensive.In view of the great application value of atomic magnetometers in many fields and the significant gap between China and abroad,it is very important to carry out the research of atomic magnetometers.In this thesis,atomic magnetometers are designd and studied,and the main works are as follows.The basic principle of the cesium magnetometer is organized and analyzed.Based on the analysis of the behavior of a single ¹³³Cs atom in an external magnetic field,the research object is gradually extended to the whole ¹³³Cs atomic ensemble,and the evolution of the ¹³³Cs atomic ensemble when interacing with the light and the magnetic field is described by using the spin polarization to characterize the ¹³³Cs atomic ensemble.By analyzing the evolution of the ¹³³Cs atomic ensemble,the basic principle of the cesium magnetometer is explained.The experimental platform of cesium magnetometer is established.A magnetic shield and a magnetic field generating device are designed,and several types of current sources are designed to drive the magnetic field generating device to produce a magnetic field of arbitrary direction,magnitude and frequency experiecd by ¹³³Cs atoms.A fixing and heating device is designed to fix and heat the spherical vapor cell and the cubic vapor cell.A programe is designed to drive the fixing and heating device to heat the vapor cell and control the temperature of the vapor cell,and another programe is designed to measure and adjust the laser frequency.Based on the designed experiment decives and programes,the experimental platform is built.Considering the influence of hyperfine structure of the ¹³³Cs atom,the magnetic response characteristics of the cesium magnetometer and the response of the cesium magnetometer to an external magnetic field of arbitrary direction are analyzed,and the corresponding theoretical models are built,which are verified by the experiments.Based on the theoretical models and experimental results,a more accurate understanding of the magnetic response characteristics and a more comprehensive understanding of the performance characteristics of the cesium magnetometer are achieved.Meanwhile,methods to minimize the influence of the hyperfine structure on the external magnetic field measurement are proposed,and shemes to extract the magnetic resonance frequency in practical applications for the radio-optical cesium magnetometer and the Bell-Bloom cesium magneteter are proposed,respectively.A technique to selectively excite spin-polarized alkali atoms in different ground-state hyperfine levels is proposed.By controlling the direction of an applied rotating magnetic field,magnetic dipole transitions can be selectively excited,and the transverse spin component of alkali atoms in either hyperfine level can be created,which are explained theoretically and verified experimentally.This technique is used to accurately measure the spin relaxation and polarization of ¹³³Cs atoms in either ground-state hyperfine level.Theoretical models for the absorption of monochromatic polarized light by ¹³³Cs atoms and for the magneto-optical rotation of linear polarized light in the medium of¹³³Cs atoms are established,respectively,which are verified by the experiments.These models are applied to the research of optical detection and optical pumping as well as optimizing the performance of the cesium magnetometer.Based on the established models,a transverse method to measure the spin polarization of alkali atoms is proposed,which can realize the accurate measurement of the spin polarization of the alkali atoms in different ground-state hyperfine levels.The influence of pump light on the spin polarization and relaxation of ¹³³Cs atoms in different ground-state hyperfine levels are studied.The rate equation of optical pumping is established and is applied to simulate the influence of pump light on the spin polarization of ¹³³Cs atoms.Using the transverse method to measure the spin polarization of alkali atoms proposed by this thesis,the influence of pump light on the spin polarization of ¹³³Cs atoms in different ground-state hyperfine levels are studied experimentally.Using the technique to selectively excite spin-polarized alkali atoms in different ground-state hyperfine levels proposed by this thesis,the influence of pump light on the spin relaxation of ¹³³Cs atoms in different ground-state hyperfine levels are studied experimentally.Two kinds of high-sensitivity cesium magnetometers are preliminarily implemented and further optimized.A high-sensitivity radio-optical cesium magnetometer and a high-sensitivity Bell-Bloom cesium magnetometer are preliminarily designed and implemented.The dependencies of the sensitivity of the two cesium magnetometers on the parameters like the intensity and frequency of the pump light,the intensity and frequency of the probe light,the magnidute of the exciting magnetic field,the duty of the square wave used to modulate the pump light,and the temperature of the vapor cell are researched,and the optimum ranges of these parameters are obtained.The performances of the implemented radio-optical cesium magnetometer and Bell-Bloom cesium magnetometer are tested under a propor experimental condition,respectively.The test results show that,the preliminarily implemented radio-optical cesium magnetometer can achieve a sensitivity of 82.5fT/?Hz,a fluctuation of the external magnetic field measurement within 2.5 pT,and a resolution of 1 pT,and the preliminarily implemented Bell-Bloom cesium magnetometer can achieve a sensitivity of 140.3 fT/?Hz,a fluctuation of the external magnetic field measurement within 2.5 pT,and a resolution of 1 pT.