Abstract
Theory and experiments on steady-state and femtosecond time-resolved optical nonlinearities in semiconductors are reviewed. A simple description of the physical processes underlying the nonlinearities is given. The discussion is focused on the spectral region around the fundamental absorption edge, and it covers coherent oscillations, the optical Stark effect as well as the bleaching of the exciton resonance with increasing excitation intensity, plasma screening and band-filling phenomena.