Ultrafast Dynamical Nonlinearities in GaAs Microstructures

Direct-gap semiconductors, such as GaAs, present strong dynamic optical nonlinearities. The saturation of their absorption caused by the photoexcitation of electron-hole pairs, and its associated nonlinear refractive index, have attracted particular interest since both effects allow the operation of optical gates and bistable devices. Since the response time of these nonlinear optical effects is governed by the relaxation dynamics of the excited states, it is important to improve our understanding of the relaxation mechanisms which influence the behaviour of electron-hole pairs.