Vectorial atomic magnetometer based on coherent transients of laser absorption in Rb vapor

We have designed and tested an atomic vectorial magnetometer based on the analysis of the coherent oscillatory transients in the transmission of resonant laser light through a Rb vapor cell. We show that the oscillation amplitudes at the Larmor frequency and its first harmonic are related through a simple formula to the angles determining the orientation of the magnetic field vector. The magnetometer was successfully applied to the measurement of the ambient magnetic field.

Figure 1

(a) Scheme of the magnetometer setup. DL: diode laser; P: polarizer; $\lambda /2$: half-wave plate; PD: photodetector; C: coil. (b) Temporal sequence of the total magnetic field component $B_{\parallel }$ along the light propagation direction and (c) corresponding laser absorption transient.

Figure 2

(a) Light and magnetic field vectors. Inset: Model atomic transition $F=1\to F^{\prime }=0$ using $x$ as the quantization axis. (b) Alternative set of coordinates used for the experiment in which the magnetic field and the wave vector are perpendicular to one of the coordinate axes.

Figure 3

Numerical prediction of transients for (a) $\varphi =0$ and (b) $\varphi =\pi /2$.

Figure 4

Comparison of ratio $b_{\omega }/b_{2\omega }$ determined by fitting the numerical simulation for a transition $(F=2\to F^{\prime }=1)$ (dots) and the prediction after Eq. (2) (line) with $\phi ={15}^{\circ }$.

Figure 5

Experimental absorption transients measured for the atomic cell in the environmental magnetic field for (a) $\varphi =0$ and (b) $\varphi =\pi /2$.

Figure 6

Experimental measurement of the environmental magnetic-field-vector components $B_{\perp }$ (red circles) and $B_{\parallel }$ (blue triangles) when an additional magnetic field along $B_{\parallel }$ is added (a constant value of ${10}^4$ nT was added to $B_{\perp }$ for clarity). Magnetic field modulus: black squares. Estimated value of $B_{\parallel }$ deduced from coil calibration: solid line.