We use a new rate-equation model for the propagation of sub-picosecond polarized optical pulses in a semiconductor optical amplifier (SOA). This model is based on the decomposition of the polarized optical field into TE and TM components that interact via the gain saturation, and accounts for two-photon absorption, free-carrier absorption, self- and cross-phase modulation, carrier heating, and spectral and spatial hole burning. For the first time, using our model, we have obtained numerical results for the nonlinear polarization rotation in pump-probe experiments with 200 fs pulses. These results are in good agreement with reported experimental measurements. © 2003 Elsevier Science B.V. All rights reserved.