Electromagnetically induced two-photon transparency in rubidium atoms

We present an experimental demonstration of electromagnetically induced two-photon transparency (EITT) in room temperature rubidium vapor. The 8S_1/2 to 5P_1/2 fluorescence is used to monitor the 5S_1/2(F = 3) to 8S_1/2(F = 3) two-photon absorption near resonance with the intermediate state 5P_3/2. A controlling pump laser beam is employed to coherently couple the 5P_3/2 and 5D_5/2 states, thus producing two dressed intermediate states which give rise to destructive interference in the two-photon transition. An induced two-photon transparency of about 80% has been obtained at resonance; our experimental findings are in good agreement with the general theory of Agarwal et al. (Phys. Rev. Lett., 77 (1996) 1039), when the appropriate spectroscopic parameters are used.