Abstract

Transient four-wave mixing (TFWM) has in recent years been a powerful tool for the study of the optical excitation and nonlinear response of excitons in bulk semiconductors' and semiconductor structures.² Optical nonlinearities due to band filling and homogeneous broadening due to exciton-exci- ton interactions¹ have been studied with ultrafast lasers. Of special interest has been the latter nonlinearity as the origin of a TFWM signal for negative time delay due to scattering of polarization (i.e., local-field effects), excitation-induced dephasing,⁴ or biexciton formation.⁵ Interference between excitations and fields at different optical frequencies can be significant in the wavemixing process for excitation by femtosecond (broadband) pulses. As a consequence, a clear interpretation of the experimental data can often be difficult.

© 1995 Optical Society of America