Employing spin noise spectroscopy of rubidium ensemble to calibrate Hall magnetometers when measuring weak magnetic fields

Abstract

Accuracy, deviation, and zero points drifting of commercial Hall magnetometers are important limiting factors and need to be calibrated, especially for measuring weak magnetic fields at micro Tesla level. Here, we present that measurement and characterization of spin noise spectroscopy (SNS) with a rubidium atomic ensemble under good magnetic shielding condition and its application for calibration of commercial Hall magnetometers. Obtaining SNS with narrow linewidth and high signal-to-noise ratio (SNR) is crucial to improve the accuracy of calibration. In experiment, we measured SNS with a rubidium vapor cell coated with paraffin on the inner wall, analyzed SNS signals and linewidth with different probe intensity and probe frequency detuning, and optimized these parameters for reducing the errors. Under different transverse magnetic fields generated by magnetic coils driven by an ultra-low noise and high-precision constant current source, SNS signals of rubidium atomic ensemble are measured. Corresponding Larmor frequency can be derived by fitting SNS signal, therefore transverse magnetic fields can be calibrated. We compared the transverse magnetic fields calibrated by SNS with those measured by the Hall magnetometer, analyzed the deviation and accuracy, and obtained calibration factor of commercial Hall magnetometer we used. This method is very simple and easily implemented, and can also be extended to calibrate commercial fluxgate magnetometers.