Atomic systems offer opportunities for noninvasive, accurate vector magnetometers that operate at ambient temperature and are conducive to miniaturization. Here, we demonstrate an unshielded three-axis vector magnetometer whose operation is based on the angle-dependent relative amplitude of cavity-enhanced magneto-optical double-resonance features in a room-temperature atomic ensemble. We determine the vector magnetic field value by sweeping the microwave frequency across all Zeeman sublevels and measuring optical transmission at seven double-resonance features, whose amplitudes vary as the orientation of the external static magnetic field (B→ext) changes with respect to the optical and microwave field polarization directions. Due to the complex dynamics of optical pumping and broadening mechanisms in the Doppler-broadened ensemble, we use a convolutional neural network model to account for details in our measurement spectra; this analysis determines the magnetic field direction with an accuracy of 1° and its amplitude with an accuracy of 56 nT measured at the near-Earth-field value of 50 μT.
Babaei et al. (Mon,) studied this question.