Optimization and vectorization of a Mz-type optically-pumped Rubidium magnetometer

TL;DR

This paper presents the development and optimization of an Mz-type optically pumped rubidium magnetometer with improved sensitivity and vector detection capabilities, suitable for geomagnetic navigation and anomaly detection.

Contribution

The study introduces a vector-capable Mz-type rubidium magnetometer with optimized parameters and enhanced sensitivity through combined system and signal processing techniques.

Findings

Sensitivity improved from 30.8 pT/Hz^{1/2} to 22.9 pT/Hz^{1/2} with feedback locking.

Achieved stable magnetic field tracking under closed-loop operation.

Implemented tri-axial modulation for vector magnetic field detection.

Abstract

Optically pumped magnetometers (OPMs) have demonstrated significant potential in weak magnetic field detection due to their high sensitivity. In this study, we developed an Mz-type optically pumped rubidium magnetometer using a paraffin-coated anti-relaxation vapor cell. The system optimization and performance characterization were conducted inside a magnetic shield. Specifically, the pump light intensity and radio-frequency (RF) magnetic field were jointly optimized by using the linewidth-amplitude ratio as the core metric. Based on the frequency-domain noise spectrum, the sensitivity in open-loop mode was measured to be approximately 30.8 pT/Hz^{1/2}. Furthermore, a closed-loop feedback locking technique was applied, reducing the measured noise floor under the tested conditions and improving the sensitivity to 22.9 pT/Hz^{1/2}, with a measured -3 dB bandwidth of 123 Hz. The dynamic characteristics were evaluated via magnetic-field step response, showing that the system could track magnetic-field changes stably under closed-loop operation. Finally, by using tri-axial modulation and frequency-domain demodulation, we overcame the scalar measurement limitation of traditional Mz magnetometers. This work realizes vector magnetic field detection and provides a technical basis for applications such as geomagnetic navigation and magnetic anomaly detection.