Physical Review A
Perturbing an electromagnetically induced transparency in a Λ system using a low-frequency driving field. II. Four-level system
Eric Wilson, Neil B. Manson, C. Wei
Abstract
The effect a perturbing field has on an electromagnetically induced transparency within a three-level $\ensuremath{\Lambda}$ system is presented. The perturbing field is applied resonant between one of the lower levels of the $\ensuremath{\Lambda}$ system and a fourth level. The electromagnetically induced transparency feature is split and this is measured experimentally for both single and bichromatic driving fields. In the single-driving-field case a density matrix treatment is shown to be in reasonable agreement with experiment and in both single and bichromatic cases the structure in the spectrum can be explained using a dressed-state analysis.