We investigated the manifestation of Rabi oscillation in the coherent dynamics of excitons in self-assembled semiconductor quantum dots. The Rabi oscillation phenomenon was directly observed as a function of the input pulse area. Furthermore, by performing wave packet interferometry in the nonlinear excitation regime, we discover a new type of quantum interference phenomenon, resulting from the interplay between Rabi oscillation and quantum interference.

We report systematic measurements of photoluminescence excitation spectra and dephasing times ͑T 2 's͒ on various excited states of hundreds of individual quantum dots ͑QDs͒. From the variation of T 2 's with the energy separation between excited states and the ground state (E rel ), we identified two distinct regions of E rel where LO phonon emission and hole relaxation via LA phonon emission play as dominat dephasing mechanisms. We also found a clear evidence of significantly slow energy relaxation in the E rel range where these phonon emission processes are suppressed due to the reduction of interaction phase space.

We present low-temperature studies of the optical properties of single CdS nanorods in relation to their morphology. Keeping track of the same nanorods in the photoluminescence (PL) study and during scanning electron microscope imaging, we were able to distinguish intrinsic spectral features of the nanorods from those of nanocluster aggregates. We observed strong PL polarization in the direction perpendicular to the nanorod axis. The sharp peaks in the “blue” region of the PL spectra are redshifted relative to those of bulk CdS and of CdS microparticles in a glass matrix. Finally, we observe a very interesting “spectral diffusion” of the main emission peaks with the following characteristics: (a) Energy–energy correlation of the two main peaks, and (b) correlation and anticorrelation between energy and intensity for the two peaks. Possible mechanisms behind this phenomenon are discussed.

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Two simple and effective far-field-optics-based methods capable of isolating photoluminescence peaks of different individual self assembled quantum dots (SAQD's) with nanometer scale precision are presented. By using these methods, we performed the temperature and electric field dependent studies on the optical properties of SAQD's. We found temperature induced inter-dot carrier transfer among neighboring quantum dots (QD's) and observed the quantum confined stark effect (QCSE).