Influence of phase modulation on two-photon coherent interaction of light pulses with resonant media

An analysis is made of the influence of the phase modulation and Stark shift of levels on the coherence of light pulses propagating in media with a two-photon resonant interaction. An analytic solution is obtained for the case of two pulses, each carrying the same number of photons. The case of arbitrary numbers of photons in light pulses is also discussed.