Research On Performance Optimization Of High Sensitivity Optically-Pumped Atomic Magnetometer

The optically-pumped atomic magnetometer is one of the quantum precision measurement techniques that has attracted considerable attention due to its low cost,small size,and high sensitivity.Particularly,with the proposal of the Spin exchange relaxation free（SERF）theory,its theoretical sensitivity can reach the femtotesla or even subfemtotesla,making it highly promising for significant applications in physics and other fields.In the thesis,the rubidium atom is used as the sensing medium,and a SERF-based single light source double cell high sensitivity optically-pumped atomic magnetometer is set up and the performance optimization methods of the magnetometer is studied.Based on miniaturization of the sensor,the sensitivity of each single cell are measured to be 30 fT/（Hz）^1/2 and 25 fT/（Hz）^1/2 respectively,while the gradient sensitivity is 15 fT/（Hz）^1/2.The main contributions of the thesis are as follows:1.Response analysis and optimization of optically-pumped atomic magnetometer.A thorough description of the magnetometer’s components is provided,including optical structure,coil structure,signal detection based on phase lock amplification,and passive magnetic shield structure.The source,direction of noise and common mode rejection ratio of magnetometer and response linewidth are theoretically studied with the aim of solving the issue that the inconsistent response of the two cells affects the gradient sensitivity of the magnetometer.Experiments are used to determine the gradient noise spectrum for various responses.According to the experimental results,a linewidth optimization method is proposed to ensure that the magnetometer can operate at the optimal point to assure high common-mode noise suppression ability.2.Crosstalk analysis and Optimization of high sensitivity optically-pumped atomic magnetometer.The magnetometer’s functionality can be impacted by modulation crosstalk.In order to research the modulation crosstalk.The coil magnetic field model and the response model are built in accordance with the response theory of the magnetometer to quantitatively assess the crosstalk.The experiment then employs a variety of frequency and amplitude modulation fields to ascertain the correlation between the modulation crosstalk and the modulation magnetic field characteristics.By employing a single field simultaneously modulates the two cells,the gradient sensitivity is improved from 50 fT/（Hz）^1/2 to 40 fT/（Hz）^1/2.3.Research on the optimization of laser heating structure of the cell in high sensitivity optically-pumped atomic magnetometer.Firstly,the multiphysics simulation software COMSOL were used to analyze the maximum temperature difference inside the cell and the laser power required for heating under various combinations of optical filters.Subsequently,experimental tests were performed to determine the laser power required for heating the cell to 150 ℃ with two different thicknesses of the front optical filter.The experimental results were then analyzed to investigate the longitudinal and transverse temperature distributions in the cell.According to the results,the optimal laser heating scheme is obtained: the heating laser and the pumping laser are orthogonal and the filters is thick at the front and thin at the back.This optimized structure ensured that the temperature gradient in the direction of the pump light remains below 7 ℃,leading to an improvement in the single-cell sensitivity from 50 fT/（Hz）^1/2 to 30 fT/（Hz）^1/2.After optimization,the sensitivity of the single-cell are to 30 fT/（Hz）^1/2 and 25 fT/（Hz）^1/2,respectively,with a gradient sensitivity of 15 fT/（Hz）^1/2.