Simultaneous coupling of three hfs components in a cascade scheme of EIT in cold 85Rb atoms

We have investigated multiple windows of electromagnetically induced transparency (EIT) registered in a cascade scheme 5S(1/2)(F = 3) -> 5P(3/2)(F = 3) <-> 5D(5/2)(F '' = 4, 3, 2) of cold Rb-85 atoms in a magneto-optical trap (MOT), with a weak probe laser in the first step and with a strong coupling laser in the second step. A structure composed of up to three transparency windows is observed in the spectral profile of the probe absorption, due to a simultaneous coupling of three F '' components of a dense hfs structure of a 5D5/2 state of the 85Rb isotope. The experimental EIT features, as dependent on the coupling beam intensity or on the frequency detuning from the F = 3 -> F = 3 resonance are compared with those theoretically obtained from a five-level model. A coefficient characterizing a relative decrease of absorption at the center of the most prominent EIT peak, plotted versus the coupling beam intensity, is also presented for both the experimental and modeled spectra. A good agreement between theory and experiment is observed. As it is very simple to manipulate the positions, shapes and depths of the EIT features, the present scheme could be of interest, e.g., for the quantum information science. (C) 2009 Elsevier B.V. All rights reserved.