  Propagation of a weak Gaussian probe pulse through a closed loop $\Lambda$
system with permanent dipole moments (PDMs) is investigated in presence of a
strong control field along with a third field. The presence of PDMs allows
multi photon excitation, which are otherwise forbidden. The PDMs modify the
Rabi frequencies of the probe, control, and the third field inside the medium
which noticeably affects the propagation of probe pulse. The probe pulse is
amplified during propagation with its Gaussian shape intact. Due to
unprohibited two photon excitation it is possible to amplify a probe pulse
whose frequency is twice of the control field's frequency, with the help of the
third field.
