Conversion between electromagnetically induced transparency and absorption in a three-level lambda system
Sapam Ranjita Chanu, Kanhaiya Pandey and Vasant Natarajana
Department of Physics, Indian Institute of Science - Bangalore 560 012, India
Accepted: 26 April 2012
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.
PACS: 42.50.Gy – Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption / 32.80.Qk – Coherent control of atomic interactions with photons / 32.80.Xx – Level crossing and optical pumping
© EPLA, 2012