Abstract

Despite recent effort,^1-5 there are aspects of the transient four-wave-mixing (TFWM) response of semiconductors that remain puzzling. As shorter pulses have been used there has appeared an apparent discrepancy between the spectral emission width and decay of the time-integrated signal.³ It has also been noted that the exciton is surprisingly dominant in the emission spectrum.⁴ By performing partially nondegenerate TFWM (PND- TFWM) we show that for broadband excitation, the signal emitted at the 1 s exciton is dominated by contributions that correspond to excitation of higher states by the first pulse. The interference of these contributions results in the rapid decay of the excitonic signal. Our results demonstrate that, because TFWM is inherently a many-particle phenomenon, the many-body interactions always couple the excitonic transitions. They also show that for broadband excitation, the decay of the time-integrated TFWM signal cannot be related to scattering.

© 1996 Optical Society of America