Author Affiliations
Abstract
1 School of Instrumentation and Optoelectronic Engineering, Beihang University, Beijing 100191, China
2 Hangzhou Innovation Institute of Beihang University, Hangzhou 310051, China
3 Beihang Hangzhou Innovation Institute Yuhang, Hangzhou 310023, China
4 Research Institute for Frontier Science, Beihang University, Beijing 100191, China
We propose a dual-mode optically pumped magnetometer (OPM) that can flexibly switch between single-beam modulation mode and double-beam DC mode. Based on a miniaturized vapor cell, the double-beam DC mode achieves a sensitivity of with probe noise below and working bandwidth over 65 Hz. This mode is designed to precisely measure the noise floor of a mu-metal magnetic shield. The single-beam modulation mode (sensitivity ) exhibits bandwidth characteristics suitable for biomagnetic measurements. Thus, our design is suitable for a miniaturized OPM with multiple functions, including magnetic-shield background noise measurement and medical imaging.
optically pumped magnetometer atomic optics dual-mode magnetometer magnetoencephalography medical imaging Chinese Optics Letters
2022, 20(8): 081202
Author Affiliations
Abstract
1 School of Instrumentation and Optoelectronic Engineering, Beihang University, Beijing 100191, China
2 Beihang Hangzhou Innovation Institute Yuhang, Hangzhou 310023, China
3 Research Institute for Frontier Science, Beihang University, Beijing 100191, China
Optically pumped magnetometers (OPMs) have developed rapidly in the bio-magnetic measurement field, which requires lasers with stable frequency and intensity for high sensitivity. Herein we stabilize a vertical-cavity surface-emitting laser (VCSEL) without any additional setup except for the parts of an OPM. The linewidth of the absorption spectrum as a frequency reference is broadened to 40 GHz owing to pressure broadening. To enhance performance, the VCSEL injection current and temperature are tuned simultaneously using a closed-loop control system. The experiments reveal that the VCSEL frequency stability achieves at an average time of 1 s, and the intensity noise is at 1–100 Hz. This approach is useful for suppressing OPM noise without additional sensor probe parts.
optically pumped magnetometer vertical-cavity surface-emitting laser single-closed-loop double-closed-loop Chinese Optics Letters
2021, 19(12): 121407
1 北京航空航天大学“惯性技术”重点实验室, “新型惯性仪表与导航系统技术”国防重点学科实验室, 北京 100191
2 上海航天控制工程研究所, 上海 200233
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。
原子吸收光谱 原子密度 气体压强 Lorentz线型 Atomic absorption spectrometry Atomic number density Pressure of buffer gas Lorentz profile
