Coherent interaction effects in probe pulse experiments

An investigation is made of resonance absorption of picosecond pulses when time-delayed approximately coUinear or exactly counterpropagating pump and probe pulses are superposed in a sample. The coherent and incoherent components of the influence of the probe beam on the absorption are calculated as a function of the delay time. In addition, the influence of phase modulation of the pump wave and emission of waves of different diffraction orders is studied.