  The electromagnetically induced transparency (EIT) phenomenon in a four level
atomic system with tripod configuration is studied. The results show that this
configuration is equivalent to the combination of two single three-level
$\Lambda$ configurations, which, under certain conditions, results in the
so-called double-EIT (DEIT) phenomenon. The properties of the double
transparency windows for DEIT are discussed in detail and the possible
experimental scheme is proposed.
