Three-level medium as a former of a series of short light pulses

We study propagation of optical radiation in a gaseous medium consisting of atoms with doublet structure of the ground state. It is shown that at small deviation of the amplitude of the wave incident at the medium from the regime of adiabatically slow variation the medium polarization becomes periodically modulated. In this case the transmitted wave acquires amplitude modulation in addition to phase modulation. Under favorable conditions this modulation transforms the input quasimonochromatic wave into a regular sequence of short pulses. We show that it is possible to generalize this scheme for more complex structure such as molecules and semiconductor constructions.