Abstract

The impulsive term, used for the description of phonon coherent excitation and stimulated scattering by ultra short light pulses, finds its origin in their very short temporal width value compared to the period of the vibrational mode concerned. We present experimental results that may be in apparent contradiction with this temporal scheme. They demonstrate the simultaneous existence of various spectral excitation processes. In fact, these conflicting behaviors are revealed by the study of polaritons which frequencies are highly sensitive to the excitation field wavevector values.

© 1998 IEEE