| We study the dynamics of excitonic states in one dimensional, dimer and trimer, and two dimensional arrangements of colloidal quantum dots using a density-matrix approach. The dots are coupled via a dipole-dipole interaction akin to the Forster mechanism. Coherent oscillations of tuned donor dots are shown to appear as plateaus in the acceptor dots, and therefore in their optical response. This behavior provides one with an interesting and unique handle to monitor the quantum state of clusters in an eavesdropping arrangement. A trimer cluster in a symmetrical loop shows steady states in a shorter characteristic time than the typical radiative lifetime of the dots. Breaking the symmetry of the loop results again in damping oscillatory states in the donor dots and plateaus in the eavesdropping/acceptor dot. The use of realistic parameters allows direct comparison with recent experiments and indicates that coherent state monitoring is possible in real experiments. Estimates of the Forster coupling VF are obtained from a microscopic description of the exciton levels in the quantum dot. We present results for different materials CdS, CdSe, GaAs, and InP as function of dot features. VF shows a nonmonotonic variation with dot sizes and a maximum value that depends on the specific dot sizes, material parameters, and dot separation. We also study the effect of the orientation factor on coherent energy transfer from a donor quantum dot to an acceptor quantum dot by calculating the polarization of the acceptor dot. We study how the measurement of the acceptor polarization can be used to determine the relative orientation between the donor-acceptor pair. We also find that Forster coupling between dots results in a polarization memory transfer. |
