Thermal Atomic Compass Based on Radially Polarized Beam

The relationship between the magnetic field direction and the spatial intensity distribution of a radially polarized light passing through a polarized thermal atom ensemble is investigated, which is intuitively presented in a polarization selection absorption effect of thermal atoms. The radially polarized light has a spatial axisymmetric polarization structure, which is set as the probe beam. If the direction of the applied magnetic field is transformed, the absorption of the alignment atomic system to special polarization components of the probe light is changed, resulting in a different absorption ratio. This allows the 3D vector direction of the magnetic field to be inferred by using only the absorption ratio and the projection coefficient of the transmission intensity pattern. Based on this, this work provides a compass based on a thermal atom system, demonstrating a new method for measuring the magnetic field direction in space.