Electromagnetically-induced transparency and light storing are studied in the
case of a medium of atoms in a double Lambda configuration, both in terms of
dark- and bright-state polatitons and atomic susceptibility. It is proven that
the medium can be made transparent simultaneously for two pulses following
their self-adjusting so that a condition for an adiabatic evolution has become
fulfilled. Analytic formulas are given for the shapes and phases of the
transmitted/stored pulses. The level of transparency can be regulated by
adjusting the heights and phases of the control fields.Comment: text +6 figure