Coherent phonon dynamics studied by impulsive stimulated Raman scattering

In the first part of this work, impulsive stimulated Raman scattering (ISRS) with tunable fs optical pulses is applied to investigate the mechanism of coherent phonon excitation in opaque materials. Comparison of theoretical values for the phonon-induced change in reflectivity as a function of photon energy in Sb with experimental data yields satisfactory agreement without the need to invoke other mechanisms of generation besides stimulated Raman scattering. In the second part, measurements of the phonon/polariton dephasing time in GaP for mode frequencies between 340 and 364 cm(-1) are presented. The experimental data are well described by a classical oscillator fit assuming anharmonic interaction with acoustic combination modes.