磁共振系统中自旋极化过程的时间特性  

Time Characteristics of Spin Polarization in Magnetic Resonance System

作　　者：董雅宾[1,2] 任磊 刘博 张熔石 杨丽 康志华[1] 马强 王彦华 DONG Ya-bin;REN Lei;LIU Bo;ZHANG Rong-shi;YANG Li;KANG Zhi-hua;MA Qiang;WANG Yan-hua(College of Physics and Electronic Engineering,Shanxi University,Taiyuan 030006,China;Collaborative Innovation Center of Extreme Optics,Shanxi University,Taiyuan 030006,China)

机构地区：[1]山西大学物理电子工程学院,山西太原030006 [2]山西大学极端光学协同创新中心,山西太原030006

出　　处：《量子光学学报》2024年第1期37-43,共7页Journal of Quantum Optics

基　　金：国家自然科学基金(61275212;11004126)。

摘　　要：本文从理论上和实验上分析了铷原子在静磁场和射频磁场作用下激光抽运磁共振系统中极化过程的时间特性。在我们的实验中,构建了简单的激光抽运实验平台,并通过记录探测光的透射强度监测铷原子的极化状态。射频场关闭时,铷原子通过吸收圆偏共振探测光实现极化,透射光强度达到最大。打开共振射频磁场,极化状态被破坏,即原子会退极化并重新吸收探测光,透射光强度减弱。实验结果表明,探测光功率会影响铷原子实现极化的过程。探测光功率越大,完成极化所需的时间越短。在70μW到200μW的探测光功率范围内,铷原子完成自旋极化的时间由33.93 ms缩短到23.37 ms。基于三能级系统的密度矩阵理论数值分析,有力地支持了所提供的实验数据。In this study,the temporal characteristics of the polarization process of rubidium atoms in a laser pumping magnetic resonance system under the influence of a constant magnetic field and radiofrequency(RF)field are analyzed both theoretically and experimentally.A simple optical magnetic resonance experiment platform has been established based on rubidium atoms in our experiment.By applying a constant magnetic field along the z-direction,Zeeman splitting was induced in rubidium atoms.The frequency of the laser propagating along the z-direction was locked to the saturated absorption spectrum of~(85)Rb atoms'D1 line transition 5~2S_(1/2),F_g=3→5~2P_(1/2),F_e=2,and converted into left circularly polarized beam to polarize the atoms.This laser beam was also used as a probe beam to detect the polarization state of rubidium atoms.Meanwhile,a switch-controlled resonant RF field was applied along the x-direction to induce transitions between atomic polarization states.Here,we monitored the polarization state of rubidium atoms by recording the transmission intensity of the probe beam.When the RF field is turned off,rubidium atoms are polarized solely by absorbing left circularly polarized probe beam.The maximum intensity of the transmitted beam indicates that maximum polarization can be achieved in the experiment.When the resonant RF field is activated,the polarization state is disrupted,causing the atoms to depolarize and reabsorb the probe beam,resulting in a decrease in the intensity of the transmitted beam.The minimum intensity of the transmitted beam indicates an equilibrium between the magnetic resonance depolarization process and the optical pumping polarization process.The RF current amplitude was set to 1.8 mA,and the probe beam power increased from 70μW to 200μW.The time evolution of transmission beam was observed by periodically switching the current amplitude of the RF coil.Experimental results showed that the power of the probe beam influenced the polarization process of rubidium atoms,with higher probe be

关 键 词：光抽运 自旋极化 密度矩阵方程 

分 类 号：O482.53[理学—固体物理]