N. H. Bonadeo

SINGLE QUANTUM DOT STATES MEASURED BY OPTICAL MODULATION SPECTROSCOPY

Using optical modulation spectroscopy, we report the direct observation of absorption lines from excitons localized in GaAs single quantum dot potentials. The data provide a measurement of the linewidth, resonance energy, and oscillator strength of the transitions, and show that states which decay primarily by nonradiative processes can be directly probed using this technique. The experiments establish this technique for the characterization of single quantum dot transitions, thereby complementing luminescence studies.

Single quantum dot states: Energy relaxation and coupling

Summary form only given. In the late 1990s, numerous groups have reported studies of the optical spectrum of individual quantum dots (QDs) successfully removing the spectral blurring caused by inhomogeneous broadening in ensemble measurements. These developments have now enabled the study of the coherent optical response and the demonstration of transient coherent control in a single QD. Most single QD experiments have used photoluminescence (PL) techniques to probe the system. Extending the methodology used to report on the resonant nonlinear optical response, we now report the measurement of the energy relaxation rate between QD states and obtain information about the nature of the state coupling. The measurements show evidence for incoherent coupling between states with fast energy relaxation. In contrast, the coupling between states belonging to the same fine structure doublet is very strong showing signatures that these states may be coherently coupled.

Coherent optical control and manipulation of semiconductor quantum dots

Summary form only given. The three dimensional confinement of excitons leads to an atomic-like optical spectrum. The discrete nature of the spectrum coupled with the highly localized nature of the excitation makes these structures ideal for new device concepts such as quantum logic devices or novel sources of non-classical radiation. While these structures are believed to have properties similar to simple atomic/molecular systems, there is the potential for large-scale integration of these structures with coherent light sources and detectors. Our work has focused on examining the electronic features of GaAs quantum dots using coherent nonlinear optical spectroscopy. The measurements extend the similarities to atomic systems demonstrating not only a nonlinear optical response distinct from that observed in higher dimensional systems, but also fast coherent optical control and features important to potential applications such as inter-dot coupling, biexcitons, and quantum entanglement.