Voigt-effect-based three-dimensional vector magnetometer

Abstract

We describe a method to dispersively detect all three vector components of an external magnetic field using alkali atoms based on the Voigt effect. Our method relies on measuring the linear birefringence of the radio frequency dressed atomic medium via polarization homodyning. This gives rise to modulated polarization signals at the first and second harmonic of the dressing frequency. The vector components of the external magnetic field are mapped onto the quadratures of these harmonics. We find that our scheme can be utilised in both cold and hot atomic gases to detect such external fields in shielded and unshielded environments. In the shielded hot vapour case we achieve field sensitivities in the pT √Hz range for all 3 vector components, using pump-probe cycles with 125 Hz repetition rate, and limited by the short coherence time of the cell. Finally, our scheme has a simple single axis beam geometry making it advantageous for miniature magnetic field sensors. arXiv:1810.08999v2 [physics.atom-ph]

Floquet description of optically pumped magnetometers

“…(2)] and can be solved by employing the Floquet expansion. This solution predicts sensitivity to all three vector components of the magnetic field as reported in the experimental work in [22]. This FIG.…”

“…On the other hand, in Ref. [22] we have shown that indeed it is possible to employ dispersive measurements based on Voigt rotation when working with aligned states driven by radio-frequency fields, also showing vector magnetometry operation (see Fig. 2).…”

“…To optically probe this kind of dynamics dispersively, we have proposed in Ref. [22] a measurement based on Voigt rotation. This effect measures the changes in the linear birefringence of the probing light (see Fig.…”

“…Given the harmonic nature of this dynamical equation, we employ a Floquet expansion of the spin operatorsF(t ) in order to find a steady-state solution for all the possible harmonics. Therefore, we expand the spin operator harmonically aŝ F(t ) =F (0) (t ) +F (1) (t ) e iωt +F (−1) (t ) e −iωt +F (2) (t ) e 2iωt +F (−2) (t ) e −2iωt + • • • , (22) such that for the first moment we have P(t ) = n P (n) (t )e inωt where P (n) (t ) = F (n) (t ) . This expansion allows to compute the dynamics of P(t ) by finding the time evolution of the harmonic components P (n) (t ).…”

“…The dynamical evolution of aligned states dressed by a radio-frequency field enables detection of all three vector components of the magnetic fields. The magnetic fields B x , B y , and B z are measured from the change in ellipticity on the probe beam and can be represented as a frame rotation from (x , y , z ) to (x, y, z) [22].…”