| Utilising a transient pump-probe reflectivity experimental system, the lattice and carrier dynamics of GaAs and InSb are explored on sub-picosecond timescales. In GaAs, the sub-200 fs behaviour of photo-excited charge carriers is observed and a model is constructed, based on the third order polarization response, to extract the time constants of carrier relaxation.; Measurements of an edge-illuminated GaAs photo-conductive (PC) switch demonstrate that carriers screen the local field within 100 fs of photo-excitation and participate in the generation of an ultrashort electrical transient. Plasmon-phonon modes produced at the longitudinal-optic (LO) and transverse-optic (TO) phonon frequencies indicate the lattice participates in the field screening process.; The first time domain observation of coherent longitudinal acoustic (LA) phonons resulting from a very high photo-generated carrier density in InSb is presented. A frequency shift of one phonon mode indicates the lattice is approaching an unstable regime for laser fluences significantly below the damage threshold. |
