Magnetic field direction detection using electromagnetically induced transparency with a vector vortex beam

We experimentally demonstrate how one can measure the magnetic field direction using electromagnetically induced transparency (EIT) with a vector vortex laser beam. Unwrapping the intensity variation along the vortex allows to simultaneously obtain information about EIT resonance amplitudes for all laser polarizations from one differential intensity image. We demonstrate that one can determine the orientation of the transverse component of the magnetic field with sub-degree precision by tracking the angular position of EIT amplitude extrema. Fourier analysis of the peaks' azimuthal dependence enables unambiguous identification of the angle between the magnetic field and the laser propagation direction (longitudinal angle). The proposed method is fully compatible with EIT-based magnetometers, and particularly attractive for integrated assemblies, since it does not require any active polarization rotators.