Abstract

Coherent phenomena in semiconductors are a sensitive probe to many-body interactions among the optically excited carriers. Recent results show that interaction between continuum states and the exciton result in modification of the excitonic coherent response. These modifications are apparent in transient-four-wave-mixing (TFWM) where the signal as function of delay decays anomalously fast compared to its spectral width.^1,2 It is also apparent as coherent emission from the exciton, even when the first pulse does not spectrally overlap it.¹ The interactions coherently couple exciton and continuum states, producing destructive quantum interference and hence the anomalous decay. Model results show the observations are consistent with the coupling being due to excitation-induced dephasing (EID).² Here we provide experimental proof that EID is the relevant coupling mechanism by performing TFWM experiments in the presence of a varying density of incoherent carriers.

© 1999 Optical Society of America