Femtosecond laser studies of the relaxation dynamics of semiconductors and large molecules

The use of femtosecond lasers and the related optical correlation spectroscopic technique for studying the relaxation dynamics of semiconductors and photoexcited molecules are reviewed. In particular, the results on the intraband relaxation of nonequilibrium carriers in GaAs and related compounds and quantum well structures are summarized. The optical correlation technique also led to the observation of quantum beats in the femtosecond time domain corresponding to the direct observation of molecular vibrations in the time domain.