Visualizing strongly focused 3D light fields in an atomic vapor

Abstract: Structured light, when strongly focused, generates highly confined vectorial electromagnetic field distributions which may feature a polarization component along the optical axis. Manipulating and detecting such 3D light fields is challenging, as conventional optical elements and detectors do not interact with the axial polarization component. Vector light can, however, be mapped onto atomic polarizations, making electric dipole transitions an ideal candidate to sense such 3D light configurations. Working in the hyperfine Paschen-Back regime, where the electric dipole transitions are spectrally resolved, we demonstrate direct evidence of the axial polarization component of strongly focused radial light. We investigate the influence of various input polarization states, including radial, azimuthal, and higher-order optical vortices, on atomic absorption profiles. Our results confirm a clear mapping between the 3D vector light and the atomic transition strength. This work provides new insights into vectorial light-matter interaction, and opens avenues for novel quantum sensing applications.