Conversion between electromagnetically induced transparency and absorption in a three-level lambda system

Abstract

We show that it is possible to change from a subnatural electromagnetically induced transparency (EIT) feature to a subnatural electromagnetically induced absorption (EIA) feature in a (degenerate) three-level Λ system. The change is effected by turning on a second control beam counter-propagating with respect to the first beam. We observe this change in the D2 line of Rb in a room temperature vapor cell. The observations are supported by density-matrix analysis of the complete sublevel structure including the effect of Doppler averaging, but can be understood qualitatively as arising due to the formation of N -type systems with the two control beams. Since many of the applications of EIT and EIA rely on the anomalous dispersion near the resonances, this introduces a new ability to control the sign of the dispersion.

Study of a four-level system in vee + ladder configuration

“…But the related phenomenon of electromagnetically induced absorption (EIA)-enhanced absorption of the probe laser-is possible only when there are at least four levels, so that additional control lasers can be used. EIA has been studied-both theoretically and experimentally-in N-type (Λ + V) four-level systems [4][5][6]. The other fourlevel systems, namely Y-type (Ξ + Ξ), inverted Y-type (Λ + Ξ), and tripod-type (Λ + Λ), only show enhanced EIT.…”

Role of different type of sub-systems in doubly driven Lambda-system in 87Rb

“…The TOC between level |1 and any general level |i is ρ 1i as shown in fig. 1, corresponds to term 1 4…”

“…

The well known Λ-system using two ground state hyperfine levels, F=1 and F=2 of 5S 1/2 and one hyperfine level, F=2 of excited state of 5P 3/2 of 87 Rb has been recently studied using two counterpropagating control lasers [1]. The experiment shows conversion of electromagnetically induced transparency (EIT) into electromagnetically induced absorption (EIA) because the doubly driven Λ-system forms various sub-systems.

…”

“…The ρ 14 corresponding to the term 1 γ13γ14 , causes induced absorption and known as a EITA. The ρ 15 corresponding to1…”

Wavelength mismatch effect in electromagnetically induced absorption

“…Such extended systems allow the possibility of electromagnetically induced absorption (EIA), a phenomenon where an initially absorbing medium shows enhanced absorption at line center. EIA has been studied-both theoretically and experimentally-primary in N-type (Λ+V) 4-level systems [3][4][5][6]. We have recently shown that EIA resonances are also possible in a new kind of 4level system made by adding vee and ladder configurations [7].…”