Propagation effects on the peak profile in two-dimensional optical photon echo spectroscopy

The effect of pulse propagation on the lineshape in a two-dimensional photon echo spectrum is investigated using the coupled Maxwell Bloch equations. Reshaping of excitation and signal pulses due to propagation results in broadening of peak profiles. The amount of broadening is not symmetric along the two dimensions and depends on pulse intensity and relaxation mechanism. It is found that relaxation mechanisms that give the same lineshape at low optical density (OD) can give different lineshapes at high OD. Even at relatively low OD the reshaping can be quite severe, and might result in misinterpretation of the obtained spectrum.