Polariton pulse propagation at exciton resonance in CuCl: Polariton beat and optical precursor

We observed polariton beats and optical precursors in propagation experiments at exciton resonance in CuCl, and obtained good agreement between experimental results and numerical calculations using a two-oscillator model. The observation of more than thirty periods of beatings enables us to determine the polariton parameters and the dephasing constants. At higher intensities we observed a suppression of the polariton beat and found that the suppression is well reproduced by excitation induced dephasing.