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

EPL (Europhysics Letters) (Impact Factor: 2.26). 02/2011; 98(4). DOI: 10.1209/0295-5075/98/44009
Source: arXiv

ABSTRACT We show that it is possible to change from a {\it subnatural}
electromagnetically induced transparency (EIT) feature to a {\it subnatural}
electromagnetically induced absorption (EIA) feature in a (degenerate)
three-level $\Lambda$ 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 $D_2$ 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.

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##### Article: Role of different types of subsystems in a doubly driven Λ system in 87Rb
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ABSTRACT: The well-known Λ system using two ground-state hyperfine levels, Fg=1 and Fg=2 of 5S1/2, and one hyperfine level, Fe=2 of excited state of 5P3/2 of 87Rb, has been recently studied using two counterpropagating control lasers [ Sapam Ranjita Chanu, Kanhaiya Pandey and Vasant Natarajan Europhys. Lett. 98 44009 (2012)]. The experiment shows conversion of electromagnetically induced transparency into electromagnetically induced absorption because the doubly driven Λ system forms various subsystems. We here present a detailed theoretical study of the different possible subsystems created by this configuration. We also explore the possibility of tuning the strength of individual subsystems by changing the polarization of the control lasers.
Physical Review A 04/2013; 87(4). · 3.04 Impact Factor