We observe large spontaneous emission rate modification of individual InAs Quantum Dots (QDs) in 2D a photonic crystal with a modified, high-Q single defect cavity. Compared to QDs in bulk semiconductor, QDs that are resonant with the cavity show an emission rate increase by up to a factor of 8. In contrast, off-resonant QDs indicate up to five-fold rate quenching as the local density of optical states (LDOS) is diminished in the photonic crystal. In both cases we demonstrate photon antibunching, showing that the structure represents an on-demand single photon source with pulse duration from 210 ps to 8 ns. We explain the suppression of QD emission rate using Finite Difference Time Domain (FDTD) simulations and find good agreement with experiment.One of the core issues of modern optics is the subject of photon interaction with matter. In the Wigner-Weisskopf approximation, the emission rate is directly proportional to the LDOS [1]. Over the past decade, photonic resonators with increased LDOS have been exploited to enhance emission rate for improving numerous quantum optical devices (e.g., [2,3]). Single photon sources in particular promise to see large improvements [4]. While more attention has been given to increasing emission rate, the reverse is also possible in an environment with decreased LDOS.Here we demonstrate that by designing a photonic crystal structure with a modified single-defect cavity, we can significantly increase or decrease the spontaneous emission (SE) rate of embedded QDs. Photonic crystals (PCs), periodic arrays of alternating refractive index, are near-ideal testbeds for such experiments. Their electromagnetic band structure modifies the LDOS relative to free space and hence the SE rate of embedded QD emitters. We demonstrate that SE of cavity-coupled QDs is enhanced up to 8 times compared to QDs in bulk GaAs. This coupling paves the way to single photon sources with higher out-coupling efficiency and visibility. On the other hand, decoupled QDs emit at up to five-fold decreased rate compared to bulk. This lifetime enhancement is significantly higher than

We optically probe and electrically control a single artificial molecule containing a well defined number of electrons. Charge and spin dependent interdot quantum couplings are probed optically by adding a single electron-hole pair and detecting the emission from negatively charged exciton states. Coulomb- and Pauli-blockade effects are directly observed, and tunnel coupling and electrostatic charging energies are independently measured. The interdot quantum coupling is shown to be mediated by electron tunneling. Our results are in excellent accord with calculations that provide a complete picture of negative excitons and few-electron states in quantum dot molecules.

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We have investigated electron filling in single InAs quantum dots (QDs) using a lateral electron transport structure, i.e., nanolithographically defined metallic leads with nanogaps. Elliptic InAs QDs with a diameter of ∼60∕80nm exhibited clear shell filling up to 12 electrons before the gate leakage became significant. Shell-dependent charging energies and level quantization energies for the s, p, and d states were determined from the addition energy spectra. Furthermore, it was found that the charging energies and the tunneling conductances strongly depend on the shell, reflecting that the electron wave functions for higher shells are more extended in space.

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We probe acoustic phonon mediated relaxation between tunnel coupled exciton states in an individual quantum dot molecule in which the inter-dot quantum coupling and energy separation between exciton states is continuously tuned using static electric field. Time resolved and temperature dependent optical spectroscopy are used to probe inter-level relaxation around the point of maximum coupling. The radiative lifetimes of the coupled excitonic states can be tuned from

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We demonstrated the first room temperature continuous wave lasing in InAs quantum-dot microdisk lasers with a standard air-cladding optical confinement structure. The spectrum shows the single strong lasing peak at a wavelength of 1280 nm. The threshold pump power is 410 muW, and the corresponding effective threshold obtained by considering the absorption efficiency is 81 muW. This achievement is mainly attributed to the increase in Q factor by the improved disk shape.