Theoretical and experimental investigations of time-dependent degenerate four-wave mixing in semiconductors

A recently developed theoretical approach to degenerate four-wave mixing (DFWM) in the Raman-Nath regime is extended to allow the analysis of pulsed DFWM experiments in laser-excited semiconductors. The full time-dependent carrier-density grating equation is solved numerically to allow the calculation of time-integrated diffraction efficiency spectra. The calculations are compared with the results of pulsed experiments performed on low-temperature CdS for a variety of excitation intensities. Qualitative agreement between experiment and theory is obtained, yielding insights into the dynamics of the nonlinear-optical properties underlying the excitation-dependent behavior of the scattering spectra.