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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 secondcontrol beam counter-propagating with respect to the first beam. We observethis change in the $D_2$ line of Rb in a room-temperature vapor cell. Theobservations are supported by density-matrix analysis of the complete sublevelstructure including the effect of Doppler averaging, but can be understoodqualitatively as arising due to the formation of $N$-type systems with the twocontrol beams. Since many of the applications of EIT and EIA rely on theanomalous dispersion near the resonances, this introduces a new ability tocontrol the sign of the dispersion.

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