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A spectroscopic method, which enables characterization of a single isolated quantum dot and a quantum wave function interferometry, is applied to an exciton discrete excited state in an InGaAs quantum dot. Long coherence of zero-dimensional excitonic states made possible the observation of coherent population flopping in a 0D excitonic two-level system in a time-domain interferometric measurement. Corresponding energy splitting is also manifested in an energy-domain measurement.

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A general scheme is established within the effective-mass approximation to calculate systematically the excitonic energy spectra in a semiconductor quantum dot including the dielectric confinement effect. This effect is found to appear most pronounced in the quantum-dot structure in comparison with the quantum-well and quantum-wire structures. A formula of the lowest exciton energy in the strong confinement regime is derived and the significance of the dielectric confinement effect is clarified. We investigate the dependence of the binding energy and the oscillator strength of the lowest-energy excitonic state on the quantum-dot radius, the electron-to-hole mass ratio, and the dielectric-constant ratio between the quantum dot and the surrounding medium. The subband mixing effect due to the electronhole Coulomb interaction gives a finite oscillator strength to excitonic transitions which are forbidden in the absence of the Coulomb interaction. This effect is shown unambiguously in the calculated excitonic energy spectra. Furthermore, the electron-hole exchange interaction in a quantum dot is discussed. The short-range part of the exchange energy is shown to increase in proportion to the inverse of the volume of the quantum dot as the quantum-dot size is reduced. On the other hand, the long-range part of the exchange energy is found to be sensitively dependent on the shape of the quantum dot. In particular, it vanishes for the optically allowed excitonic states in a spherical quantum dot.

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.