Abstract

We report polarization dependent nonlinear optical studies in homogeneously broadened GaAs quantum wells. The measurements show surprisingly that biexcitonic effects are the dominant contribution in both differential transmission and self-diffracted four wave mixing (FWM) where the two incident pulses are cross-linearly polarized. Although biexcitonic effects have attracted considerable efforts recently, the importance of the biexcitonic contribution to nonlinear responses has not been appreciated. Our results indicate that the correlation between excitons with opposite spins plays an important role in nonlinear optical interactions and the current understanding based on the semiconductor Bloch equation is inadequate. Furthermore, extension of the result to inhomogeneously broadened systems explains the anomalous polarization dependence in FWM [1], including the observation of free polarization decay in inhomogeneously broadened quantum wells.

© 1994 Optical Society of America