The nonlinear optical response of interacting charge-transfer excitons with a weak probe in a strong pump field

The nonlinear optical response of interacting charge-transfer excitons is i nvestigated theoretically by means of pseudospin operators for the model Ha miltonian. The generalized optical Bloch equations including the static dip olar interaction of charge-transfer excitons are derived in terms of the He isenberg equation of motion and the mean-field approximation. It is shown t hat the intrinsic optical bistability due to the strong interaction of char ge-transfer excitons may exist in the interacting charge-transfer exciton s ystem. The absorption spectrum of interacting charge-transfer excitons asso ciated with a weak probe field in the presence of a strong pump field is al so calculated using the linear-response theory. The results show that a gai n without population inversion can be observed in the interacting charge-tr ansfer exciton system.