Optical responses of one-dimensional exciton system in correlated random potentials

Urbach tails at absorption edge and photon echo signals are theoretically investigated for one-dimensional exciton systems which have correlated random potentials. As two limits, these correlated random potentials include inhomogeneous distribution of energy levels and random distribution of site-energies for excitons. It is shown that spectral profile of the optical responses reflects the continuous change of the correlated potentials between the two limits.