title: Sub-Doppler absorption narrowing in atomic vapor at two intense laser fields.
abstract: We have experimentally studied electromagnetically induced transparency (EIT) and absorption (EIA) in hot 85Rb atomic vapor using probe and coupling light with comparable power levels. We have shown that strong-probe EIT has different linewidth and appears in fewer configurations than does usual, weak probe EIT. In V-scheme, where optical pumping and saturation are dominant mechanisms, narrow EIT is possible only when a probe is tuned to a closed transition. The width of the EIT resonance increases with laser intensity with non-linear dependence, similar to the weak-probe EIT in Lambda- scheme. The EIT in Lambda- scheme was observed when two transitions had balanced population losses. The EIA was modified for the case of a strong probe as well: in four-level N-scheme with Zeeman sublevels the EIA was observed only for a cycling transition when F'=F+1, where F and F' are the angular momenta of the 5 2S1/2 (ground) and 5 2P3/2 (excited) state hyper-fine levels, respectively. The combination of strong probe and strong coupling laser beam intensities allows observation of an absorption dip due to three-photon resonance in a four-level scheme that involves the Raman transitions via virtual level.
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Krmpot
authors.forename: Marina
authors.initials: M
authors.lastname: Mijailović
authors.forename: Bratimir
authors.initials: B
authors.lastname: Panić
authors.forename: Dragan
authors.initials: D
authors.lastname: Lukić
authors.forename: Aleksander
authors.initials: A
authors.lastname: Kovacević
authors.forename: Dejan
authors.initials: D
authors.lastname: Pantelić
authors.forename: Branislav
authors.initials: B
authors.lastname: Jelenković