Dynamic range and linearity improvement for zero-field single-beam atomic magnetometer

Zero-field single-beam atomic magnetometers with transverse parametric modulation for ultra-weak magnetic field detection have attracted widespread attention recently. In this study, we present a comprehensive response model and propose a modification method of conventional first harmonic response by introducing the second harmonic correction. The proposed modification method gives improvement in dynamic range and reduction of linearity error. Additionally, our modification method shows suppression of response instability caused by optical intensity and frequency fluctuations. An atomic magnetometer with single-beam configuration is built to compare the performance between our proposed method and the conventional method. The results indicate that our method's magnetic field response signal achieves a 5-fold expansion of dynamic range from 2 nT to 10 nT, with the linearity error decreased from 5% to 1%. Under the fluctuations of 5% for optical intensity and ±15 GHz detuning of frequency, the proposed modification method maintains intensity-related instability less than 1% and frequency-related instability less than 8% while the conventional method suffers 15% and 38%, respectively. Our method is promising for future high-sensitive and long-term stable optically pumped atomic sensors.     

Determination of Atomic Number Densities of ^87Rb and ^3He Based on Absorption Spectroscopy

The atomic number densities of ^87 Rb vapor and surrounding gas 3He in a sealed cubic cell were measured by sweeping the absorption line and fitting the experimental data with a Lorentzian profile. The absorption was carried out around the D1 transition at different temperatures. We compare our results for the number density for^87 Rb with the previous methods and calculate the fractional error to be less than 5% as well as the error for ^3He between this work and the density obtained from the filling procedure to be no more than 4.2% at 370K. In addition, we discuss the factors that contribute to the error, among which the cell temperature plays the most important role.     

原子吸收光谱对碱金属原子蒸气密度与压强的测量方法

利用SERF原子自旋效应能够实现高灵敏度的磁场测量,碱金属原子密度与缓冲气体压强是敏感表头碱金属气室的重要参数,需要精确地测量。提出一种应用原子吸收光谱对碱金属蒸气的原子密度与压强测量方法,通过扫描碱金属原子的吸收光谱,进行Lorentz线型拟合,经解算同时得到原子密度和压强,一次实验获得两个物理量。由于多普勒展宽和压力展宽主要受到碱金属气室温度和缓冲气体压强的影响,从这两个方面进行了仿真分析。结果表明,充入2 amg缓冲气体时,313～513 K温度范围内的Lorentz线型与Voigt线型计算的光子吸收截面积峰值的理论误差始终小于0.015%;缓冲气体压强高于0.6 amg(393 K)时,其峰值误差小于0.1%,表明该条件下多普勒展宽对吸收光谱的影响可以忽略,可用Lorentz线型拟合原子的吸收谱线。最后分析了该方法能够获得的理论分辨率以及激光器的功率波动、波长波动和气室温度波动对测量精度的影响,得出同等条件下温度波动的影响比其他两个因素高1~2个数量级。