Properties Of Quantum Dot Molecules Research Articles

Study of the linear and nonlinear optical properties of quantum dot molecules‎: Tunneling induced transparency

Study of the linear and nonlinear optical properties of quantum dot molecules‎: Tunneling induced transparency

Phase and Amplitude Control of Optical Properties of Quantum Dot Molecules

We investigate the optical properties of a weak probe field in an asymmetry semiconductor double QDs system. We apply a coupling and a probe field to the system and it is shown that in the presence of interdot tunneling, the dispersion and absorption properties of the system can be controlled by the amplitude and relative phase of applied fields. Moreover, it is demonstrated that just by changing the relative phase of applied fields, the slope of dispersion is changed from positive to negative, corresponding to the superluminal light propagation.

Circularly organized quantum dot nanostructures of Ge on Si substrates

A novel circularly arranged structure of germanium quantum dots has been fabricated by combining techniques including electron beam lithography, wet etching and molecular beam epitaxy. It was observed that both pattern and growth parameters affect the morphology of the quantum dot molecules. Meanwhile, the oxidation mask plays a vital role in the formation of circularly organized quantum dots. The experimental results demonstrate the possibilities of investigating the properties of quantum dot molecules as well as single quantum dots.

Essential concepts in the optical properties of quantum dot molecules

Here we review the basic optical spectra of quantum dot molecules. We apply a simple and straightforward model to calculate charge stability regions in vertically coupled double dot molecules that are embedded in a Schottky diode. This model allows us to relate features in the optical spectrum to the diode structure. The underlying concepts allow one to design quantum dot molecules functionalized for optical operations.

Phonon-Assisted Excitation Transfer in Quantum Dot Molecules

Coupled quantum dots (QDs), referred to as quantum dot molecules (QDMs), have attracted much attention in recent years [1]. Besides the electronic coupling or superradiance effects [2], the properties of QDMs are affected by phonon-related phenomena. In particular, many experiments have shown phonon-assisted excitation transfer [3] between the QDs. For moderate separations between the dots (6 nm) tunneling is exponentially suppressed and the energetically lowest states correspond to spatially direct excitons localized in individual QDs [4]. Such states are bound by the Coulomb interaction via interband dipole moments [5], i.e., by the Forster interaction [6]. Signatures of such coupling were indeed found in a photon-correlation experiment [7]. In this paper we derive a quantum-kinetic description of the evolution of an exciton in a QDM, including the effect of the carrier–phonon coupling. We show that, depending on the parameters, the system can show different dynamical scenarios, ranging from partial pure dephasing to an almost exponential transfer. As we shall see, the transfer may be very fast (on the timescales of several picoseconds), that is, 2–3 orders of magnitude faster than suggested by the existing perturbative estimates [8].