Nonlinear optical response by spatially separated light beams in a condensed exciton system

We present a theory of the spatially and the temporally resolved nonlinear optical response of condensed exciton systems. Our analysis is based on the nonlinear Schrodinger equation for condensed excitons coupled with two spatially separated light beams. The nonlinear optical signal is observed at the middle part between the excitation spots. It is shown that the space-resolved signal arises mainly from the nonlinear interaction between two exciton macroscopic wave functions propagating out from the excitation spots. (C) 2000 Elsevier Science B.V. All rights reserved.