Multiple peaks due to EIT and Autler-Townes effect in lambda-probing of the strongly driven 5P 3/2 manifold of cold85Rb atoms in MOT

Abstract

Electromagnetically induced transparency (EIT) and Autler-Townes (A-T) effect were studied under conditions of strong coupling of the hyperfine manifold 5P_3/2 (F') with the 5S _1/2 (F=2) ground state of cold 85Rb atoms in MOT. Transmission spectra of a weak probe beam, at the frequency scanned in the vicinity of the 5S_1/2(F=3)→5P3/2(F') resonances were registered at various frequency settings of the coupling beam. The spectra were interpreted by applying optical Bloch equations. As a starting point, a 5-level model, accounting for F=2, 3 and F'=1, 2, 3 states was assumed (the noncoupled state F'=4 being neglected, but the F'=1 state, coupled but not directly probed, included, as its presence was found to be imprinted in the spectra). Such a model alone does not reproduce all the spectral features observed. Therefore we have considered the existence of the polarized light induced transitions between Zeeman substates, involving (F'=2, m') and (F'=3, m') upper states. In order to indirectly account for the m→m' absorption transitions to the non-coupled m' states, and to the pairs of states with incomplete coupling, we have complemented the results of the 5-level model with the ones of its reduced versions. Satisfactory agreement of the positions of respective modeled and experimental spectral peaks was achieved.