All-Optical Vector Atomic Magnetometer

TLDR

The magnetometer is intended for magnetically sensitive fundamental physics experiments, including searches for a neutron permanent electric dipole moment. The study demonstrates an all‑optical magnetometer that measures both magnitude and direction of magnetic fields via nonlinear magneto‑optical rotation in cesium vapor. Vector capability is achieved by modulating the field along orthogonal axes using the ac Stark shift from circularly polarized lasers and demodulating the resulting magnetic‑resonance frequency. The sensor achieves an rms noise floor of ~65 fT/√Hz for field magnitude and 0.5 mrad/√Hz for direction, with potential improvements to 12 fT/√Hz and 10 µrad/√Hz by eliminating technical noise.

Abstract

We demonstrate an all-optical magnetometer capable of measuring the magnitude and direction of a magnetic field using nonlinear magneto-optical rotation in cesium vapor. Vector capability is added by effective modulation of the field along orthogonal axes and subsequent demodulation of the magnetic-resonance frequency. This modulation is provided by the ac Stark shift induced by circularly polarized laser beams. The sensor exhibits a demonstrated rms noise floor of $\ensuremath{\sim}65\text{ }\text{ }\mathrm{fT}/\sqrt{\mathrm{Hz}}$ in measurement of the field magnitude and $0.5\text{ }\text{ }\mathrm{mrad}/\sqrt{\mathrm{Hz}}$ in the field direction; elimination of technical noise would improve these sensitivities to $12\text{ }\text{ }\mathrm{fT}/\sqrt{\mathrm{Hz}}$ and $10\text{ }\text{ }\ensuremath{\mu}\mathrm{rad}/\sqrt{\mathrm{Hz}}$, respectively. Applications for this all-optical vector magnetometer would include magnetically sensitive fundamental physics experiments, such as the search for a permanent electric dipole moment of the neutron.