Submillimeter-resolution magnetic field imaging with digital micromirror device and atomic vapor cell

Abstract

Magnetic field source localization and imaging happen at different scales. The sensing baseline ranges from meter scale, such as magnetic anomaly detection, to centimeter scale, such as brain field imaging, to nanometer scale, such as the imaging of a magnetic skyrmion and single cell. Here, we show how an atomic vapor cell can be used to realize a baseline of 109.6 μm with a magnetic sensitivity of 10 pT/Hz1/2 @0.6–100 Hz and a dynamic range of 2062–4124 nT. We used a free induction decay (FID) scheme to suppress low-frequency noise and avoid scale factor variation for different domains due to light non-uniformity. The measurement domains are scanned by a digital micromirror device. The currents of 22, 30, 38, and 44 mA are applied in the coils to generate different fields along the pumping axis, which are measured respectively by fitting the FID signals of the probe light. The residual fields of every domain are obtained from the intercept of linearly fitting of the measurement data corresponding to these four currents. The coil-generated fields are calculated by deducting the residual fields from the total fields. The results demonstrate that the hole of shield affects both the residual and the coil-generated field distribution. The potential impact of field distribution measurement with outstanding comprehensive properties of spatial resolution, sensitivity, and dynamic range is far-reaching. It could lead to capability of 3D magnetography for small things and/or organs in millimeter or even smaller scale.

Analytical model for calculation of the magnetic field of triaxial uniform coils in magnetically shielded cylinder

“…Furthermore, the fluxgate may be too large to be installed in miniature integrated atomic sensors. Because of this problem, some researchers proposed the realization of in-situ measurement of the coil magnetic field using the atomic spin effect [18]. Zhang et al calibrated the coil magnetic field via extraction and analysis of the Larmor precession frequency of hyperpolarized 3 He in an atomic magnetometer [19].…”

A Multi-Pass Optically Pumped Rubidium Atomic Magnetometer with Free Induction Decay

“…A high measurement bandwidth was obtained whilst maintaining good sensitivity in a continuous sampling mode; this was helpful for further applications in magnetometers or sensor arrays with high measurement bandwidth requirements. H. F. Dong et al [ 21 ] demonstrated a distributed magnetic field measurement scheme based on FID magnetometer. The magnetic sensitivity reached 10 pT/ in a bandwidth of 0.6–100 Hz.…”