Sources of heading errors in optically pumped magnetometers operated in the Earth's magnetic field

Abstract

When optically pumped magnetometers are aimed for the use in Earth's magnetic field, the orientation of the sensor to the field direction is of special importance to achieve accurate measurement result. Measurement errors and inaccuracies related to the heading of the sensor can be an even more severe problem in the case of special operational configurations, such as for example the use of strong off-resonant pumping. We systematically study the main contributions to the heading error in systems that promise high magnetic field resolutions at Earth's magnetic field strengths, namely the non-linear Zeeman splitting and the orientation dependent light shift. The good correspondence of our theoretical analysis to experimental data demonstrates that both of these effects are related to a heading dependent modification of the interaction between the laser light and the dipole moment of the atoms. Also, our results promise a compensation of both effects using a combination of clockwise and counter clockwise circular polarization.

Measurement of the polarization‐ and orientation‐dependent scalar, vector, and tensor light shifts in 87Rb using the near‐resonant, stimulated Raman spectroscopy

“…The solid lines in Figure a are the fitted sinusoidal curves of the measured results that write where ( m F = − 1,0,1) is in the unit of Hz, whereas θ is in the unit of rad. Based on the fitted results in Equation , the absolute magnetic field is extracted as B eff = 78.84 nT using the method proposed by Oelsner et al and Hu et al; thus the Zeeman frequency shift of the ω 1, 1 ( ω −1, − 1 ) transition peak is δ Zeeman = 1,103.74 Hz (−1,103.74 Hz). The Doppler shifts are calculated as δ D = 6.15 Hz for the three resonant frequencies using the Raman laser's effective wave vector and the atomic velocity at 0.4 s after launch, and the angles θ k and α 0 of the effective magnetic field vector are extracted as 3.4° and 80.54° by comparing Equation with Equation .…”

“…In our previous study, we presented the frequency‐dependent SVT dynamical polarizabilities and measured the vector and tensor dynamical polarizabilities between the 5s ground‐state sublevels interacting with a pair of circularly polarized lasers. A recent study had demonstrated that the major heading error sources of the optically pumped magnetometers are the nonlinear Zeeman splitting and the orientation‐dependent LS.…”

Performance analysis of an optically pumped magnetometer in Earth’s magnetic field

“…On the one hand, the measured resonance frequencies are strongly modified by the light shift due to the intense off-resonant pumping. This effect has been extensively studied [6,7,9,24] and we use the method presented in Ref. [6] for a description of our data.…”

“…Ref. [6]) as well as an additional factor of |cos α|. Also, we did not include the linear polarized component scaling with sin α that, in principle, can also contribute to a population difference.…”

“…With the pump beam an additional direction dependence is introduced leading besides dead zones also to unwanted effects usually summarized under the label "heading error" [5]. These effects can be understood from the change in the atom-light coupling that is in dipole approximation given by the scalar product of the laser's electric field and the atoms electric dipole moment [6]. Suppression of the heading error is intensively studied [7][8][9] and it has important consequences in the application of OPMs [10,11].…”