The excitation power dependence of the ground and excited state transitions in type-II InAs-GaAs0.78Sb0.22 quantum dot structure has been studied. Both transitions exhibit a strong blueshift with increasing excitation power but their separation remains constant. This behavior indicates a carrier-induced electric field oriented predominantly along the growth axis, which requires the holes to be localized in the GaAsSb above quantum dots. An accelerated blueshift of the ground state emission is observed once the excited state in the dots starts to populate. This behavior can be explained by a smaller spontaneous recombination coefficient for the excited state transition.

Solid-state cavity quantum electrodynamics systems will form scalable nodes of future quantum networks, allowing the storage, processing and retrieval of quantum bits, where a real-time control of the radiative interaction in the cavity is required to achieve high efficiency. We demonstrate here the dynamic molding of the vacuum field in a coupled-cavity system to achieve the ultrafast nonlocal modulation of spontaneous emission of quantum dots in photonic crystal cavities, on a timescale of ~200 ps, much faster than their natural radiative lifetimes. This opens the way to the ultrafast control of semiconductor-based cavity quantum electrodynamics systems for application in quantum interfaces and to a new class of ultrafast lasers based on nano-photonic cavities.

The use of a GaAsSb metamorphic buffer layer (MBL) is demonstrated to significantly enhance the room-temperature photoluminescence intensity for 1.55μm metamorphic InAs∕GaAs quantum dots (QDs) in comparison with a conventional InGaAs MBL. A dramatic reduction of QD photoluminescence emission efficiency above 1.5μm has been observed at room temperature when the indium composition in the InxGa1−xAs MBL is increased over x=0.25. By using a GaAsSb buffer instead of InGaAs, we demonstrate a strong enhancement of photoluminescence intensity of InAs∕GaAs QDs. The effects of the GaAsSb MBL can be understood in terms of smoothing the surface morphology of the buffer layer and, hence, suppressing the formation of dislocations in the QD region. These results suggest an alternative approach to developing GaAs-based light sources in the telecommunication-wavelength range near 1.55μm.

Self-assembled InAs/GaAs quantum dots ͑QDs͒ incorporated in an asymmetric GaAs/ Al 0.8 Ga 0.2 As vertical cavity have been employed as an optical nonlinear medium for reflection-type all-optical switches. Switching time down to 23 ps together with wavelength tuning range over 30 nm have been achieved in this structure. An angle-dependent behavior of the switching time has been observed, which suggests there is a coupling mechanism between the ground and excited states in QDs with different sizes.