Carrier dynamics model of fast refractive index changes in semiconductor laser amplifiers

Recent pump probe measurements of the fast optical response of semiconductor laser amplifiers are modelled using a density matrix approach in the relaxation approximation. The results obtained with the model in a variety of situations covering the three regimes below, at and above transparency are examined in terms of the optical response and the underlying carrier dynamics. The essential features of the optical response are explained using a simple physical picture and good qualitative agreement with experiment is demonstrated