Optimization Of Parameterized Factors Of Spin Exchange Relaxation Free Regime For All-Optical Atomic Magnetometer

Spin-Exchange-Relaxation-Free(SERF)atomic magnetometer has achieved ultrahigh sensitivity because of the elimination of spin exchange collision broadening and enhancement of alkali atomic spin coherence.Combined with gradiometric and tensorial measurement,the atomic magnetometer is applied into many fields such as mineral prospecting,magnetism mapping,and maritime survey.As of now,researches on the effecting factors of spin-exchange relaxation free regime,interaction of factors with SERF regime,and the controller and monitor about experimental conditions are rarely concomitant on the extant references.With the detected demands for different fields,we could demodulate the single axis,double axes,and triaxial components of magnetic fields by applying different forms of modulated magnetic fields to the atomic spin;we could develop the experimental controller and monitor by investigating the coherent alkali-atomic spin status,such as the forming mechanics and ambient conditions of spin-exchange relaxation free regime;we could determine the optimal operating conditions by simulating the variable process of peculiarities of spin-exchange relaxation free regime caused by variation of effecting factors.Therefore,based on the significance of spin-exchange relaxation free regime,this paper delves the principal of atomic magnetometer,simulates and optimizes the affecting factors of atomic spin coherence,all with the goals providing theoretical supports and simulated validation for construction of SERF atomic magnetometer and achievement of ultrahigh sensitivity.Firstly,we performed the frequency response of alkali atoms to different forms of magnetic fields.The basic principle of the atomic magnetometer is briefly analyzed.The quantum behavior and dynamics of atomic spin are introduced from the energy level structure of alkali metal atom,optical pumping process,Larmor precession process of macroscopic magnetic moment,and light detection process.Then,from the analytical solution of the Bloch equation,the mathematical model is used to introduce and demonstrate several different operational models of the atomic magnetometer.Finally,the responses of atomic spin to different forms of the magnetic field are introduced and reasonably explained from both the quantum behaviors of alkali atoms and mathematical analysis.We delved the mechanics and peculiarities of spin-exchange relaxation free regime.Several different types of relaxation leading to magnetic resonance linewidth are firstly analyzed,including spin-exchange relaxation,spin destruction relaxation,collision relaxation caused by gas walls,and their external determinants.This thesis analyzes the effect that the spin exchange collision rate has on broadening contribution of spin exchange collision to magnetic resonance line and precession frequency by density matrix and perturbation theory and investigates the peculiarities of SERF regime including linewidth of magnetic resonance and precession frequency and the relationship between them,providing the theoretical support for determination on the alkali atoms status.Then,this paper introduces the key variables of the SERF regime: temperature,magnetic field,and polarization,then analyzes the effects three factors have on the line width of magnetic resonance and precession frequency.We simulate the decaying process of pumping intensity when pumping light goes through the cell,the relation between polarization and signal to noise ratio,and the relation between polarization and gyromagnetic ratio yielding the optimal value of polarization;We also simulate the variation of spin exchange broadening,spin destruction broadening and width of magnetic resonance line along with the temperature increasing,attaining the optimal temperature value(width of magnetic resonance line is most narrow);We simulate the effect of temperature on gyromagnetic ratio,providing valid evidence for the innovation to determine the status of alkali atoms;We simulate the effects of magnetic field on spin-exchange broadening and gyromagnetic ratio,proffering cogent theoretical support for the possibility of application of atomic magnetometry in movable platform.Finally,we simulate the mutual effect of all the factor including magnetic field,temperature,and polarization,seeking for the optimal status of alkali atoms and optimizing the performances of the atomic magnetometer.Finally,we conducted the experimental validation of factors and the tests on atomic magnetometer sensitivity.For the starters,we perform the experiments of the parameterized factors of SERF regime,obtaining the measured data of and of.It turns out that our experimental results agree well with the theoretical analysis and numerical simulation.Then,based on the peculiarities of SERF regime,the determination for identifying the status of alkali atoms is put forth which could take place of the conventional method and finish the measurement in a fast and straightforward manner so that it can avoid the draft errors and improve the measurement precision.The concrete method is organized as follows.We get the oscillating frequency of precession by decaying oscillating curves and fit the slope of curves named relation between oscillating frequency and magnetic field which indicates the gyromagnetic ratio under specific temperature condition.We compare the experimental results with theoretical analysis and numerical simulation,and it turns out that they agree well with each other except that the reasonable disparity caused by temperature.Lastly,the width of magnetic resonance line under the temperature condition of 184? is measured as 25 Hz,which indicates the broadening of spin exchange collision has been totally eliminated and the sensitivity of the whole operating system is confirmed as10(?).