Transport and correlated fluctuations in the nonlinear optical response of excitons

Closed expressions are derived for the femtosecond four-wave mixing of excitons which include slow Gaussian diagonal fluctuations (spectral diffusion) through the cumulant expansion and incoherent exciton transport induced by fast Markovian fluctuations. The interplay of both processes in the two-dimensional photon echo is demonstrated using model calculations for a dimer. Copyright (C) EPLA, 2007.