Sign reversal of Hanle electromagnetically induced absorption with orthogonal circularly polarized optical fields

We study by computation and experiment an electromagnetically induced absorption resonance in the Hanle configuration with a transverse magnetic field on a closed Fg → Fe = Fg+1 transition with co-propagating orthogonal circularly polarized probe and coupling optical fields. At high coupling field intensities, the Hanle resonance changes sign due to a shift in atomic population from Zeeman sublevels associated with a probe field cyclic transition to sublevels associated with a coupling field cyclic transition at zero magnetic field. We also show that a similar sign reversal does not occur for π-polarized and σ-polarized coupling fields.