The twisted light modes used in modern atomic physics experiments can be contaminated by small admixtures of plane-wave radiation. Although these admixtures hardly reveal themselves in the beam-intensity profile, they may seriously affect the outcome of high-precision spectroscopy measurements. In the present study we propose a method for diagnosing such a plane-wave contamination which is based on the analysis of the magnetic sublevel population of atoms or ions interacting with the “twisted + plane-wave” radiation. In order to theoretically investigate the sublevel populations, we solve the Liouville–von Neumann equation for the time evolution of the atomic density matrix. The proposed method is illustrated for the electric dipole 5sS1/22−5pP3/22 transition in Rb induced by (linearly, radially, or azimuthally polarized) vortex light with just a small contamination. We find that even tiny admixtures of plane-wave radiation can lead to remarkable variations in the populations of the ground-state magnetic sublevels. This opens up new opportunities for diagnostics of twisted light in atomic spectroscopy experiments.

• Received 13 October 2023
• Accepted 26 January 2024

DOI:https://doi.org/10.1103/PhysRevA.109.033103