We report the first systematic study of the frequency dependence of optical nonlinearities of bulk GaAs at room temperature. In contrast to the previous understanding, band filling and plasma screening of Coulomb enhancement of continuum states are found to be the dominant contributions to the dispersive optical nonlinearities under quasi steady-state excitations. The partly phenomenological semiconductor plasma theory is in good agreement with the experimental data.

• Received 6 June 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.2446