Abstract

Studying saturated-absorption of the Na D₁ line with appropriate beam polarisations (pump almost circular σ⁺ with controlled weak admixture of σ⁻ component, probe circular σ⁻), new spectral features are observed. In addition to the usual Doppler-free resonances, related to the F_g=2 ⟹ F_e=1,2 hfs transition, a new narrow line is observed between the F_g=2 ⟹ F_e=1 and the cross-over signals. The resonance corresponds to the reduction of the absorption (electromagnetically-induced transparency) and has very unusual properties: its width depends on the pump beam ellipticity (the less circular the pump, the broader the resonance); the resonance position seems to be independent of the pump beam power, but does depend very strongly on the intensity of a longitudinal magnetic field. This dependence, shown by dots in fig. 1. can be more than one order of magnitude stronger than the Zeeman splitting, marked as the dashed line there.

© 1998 IEEE