Electromagnetically induced transparency with degenerate atomic levels

For the coherently driven Λ-type three-level systems the general expression for the susceptibility tensor at the frequency of the weak probe field is obtained for the arbitrary polarization of the strong coupling laser field and arbitrary values of the angular momenta of resonant atomic levels. The dependence of the relative difference in the group velocities of the two polarization components of the probe field on the polarization of the coupling field is studied. (paper)