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Plasmonics offers the opportunity of tailoring the interaction of light with single quantum emitters. However, the strong field localization of plasmons requires spatial fabrication accuracy far beyond what is required for other nanophotonic technologies. Furthermore, this accuracy has to be achieved across different fabrication processes to combine quantum emitters and plasmonics. We demonstrate a solution to this critical problem by controlled positioning of plasmonic nanoantennas with an accuracy of 11 nm next to single self-assembled GaAs semiconductor quantum dots, whose position can be determined with nanometer precision. These dots do not suffer from blinking or bleaching or from random orientation of the transition dipole moment as colloidal nanocrystals do. Our method introduces flexible fabrication of arbitrary nanostructures coupled to single-photon sources in a controllable and scalable fashion.

We demonstrate an all-electrically operated wavelength-tunable on demand single-photon source for the first time. The device consists of a light-emitting diode in the form of a semiconductor nanomembrane containing self-assembled quantum dots integrated onto a piezoelectric crystal. Triggered single photons are generated via injection of ultrashort electrical pulses into the diode, while their energy can be precisely tuned over a broad range by varying the voltage applied to the piezoelectric crystal. High speed operation of this single-photon-emitting diode up to 0.8 GHz is demonstrated. These results represent an important step toward the realization of electrically driven sources of indistinguishable photons on demand.

We integrate resonant-cavity light-emitting diodes containing quantum dots onto substrates with giant piezoelectric response. Via strain, the energy of the photons emitted by the diode can be precisely controlled during electrical injection over a spectral range larger than 20 meV. Simultaneously, the exciton fine-structure-splitting and the biexciton binding energy can be tuned to the values required for entangled photon generation., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Increasingly complex structures such as optical antennas or cavities are coupled to self-assembled quantum dots to harvest their quantum-optical properties. In many cases, these structures pose a problem for common methods of ultrafast spectroscopy used to write and read out the state of the quantum dot. We present a pure far-field method that only requires optical access to the quantum dot and does not impose further restrictions on sample design. We demonstrate Rabi oscillations and perturbed free induction decay of single GaAs quantum dots that have a dipole moment as small as 18 D. Our method will greatly facilitate ultrafast spectroscopy of complex quantum-optical circuits., (© 2011 American Chemical Society)

We demonstrate how the controlled positioning of a plasmonic nanoparticle modifies the photoluminescence of a single epitaxial GaAs quantum dot. The antenna particle leads to an increase of the luminescence intensity by about a factor of 8. Spectrally and temporally resolved photoluminescence measurements prove an increase of the quantum dot’s excitation rate.

Arrays of GaAs microring optical resonators with embedded InGaAs quantum dots (QDs) are placed on top of Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) piezoelectric actuators, which allow the microcavities to be reversibly "stretched" or "squeezed" by applying relatively large biaxial stresses at low temperatures. The emission energy of both QDs and optical modes red- or blue- shift depending on the strain sign, with the QD emission shifting more rapidly than the optical mode with applied strain. The QD energy shifts are used to estimate the strain in the structures based on linear deformation potential theory and the finite element method. The shift of the modes is attributed to both the physical deformation and the change in refractive index due to the photoelastic effect. Remarkably, excitonic emissions from different QDs are observed to shift at different rates, implying that this technique can be used to bring spatially separated excitons into resonance.

Triggered single-photon emission from a single CdTe quantum dot (QD) grown on Si(001) substrate is demonstrated for the first time. The emission wavelength of QDs can be tuned in a wide spectral range (more than 8 meV) using a focused laser beam. A nearly perfect single-photon emission from the exciton lines is preserved even after energy tuning. The lifetime is also measured before and after laser processing, and no appreciable change is observed.

Scanning probe microscopy combined with selective wet chemical etching is employed to quantitatively determine the full three-dimensional (3D) composition profiles of single strained SiGe/Si(001) islands. The technique allows us to simultaneously obtain 3D profiles for both coherent and dislocated islands and to collect data with large statistics. Lateral and vertical composition gradients are observed, and their origin is discussed. X-ray scattering measurements performed on a large sample area are used to validate the results.

Abstract We report on the growth and characterization of lateral InAs/GaAs (001) quantum-dot molecules (QDMs) suitable for single QDM optical spectroscopy. The QDMs, forming by depositing InAs on GaAs surfaces with self-assembled nanoholes, are aligned along the [] direction. The relative number of isolated single quantum dots (QDs) is substantially reduced by performing the growth on GaAs surfaces containing stepped mounds. Surface morphology and X-ray measurements suggest that the strain produced by InGaAs-filled nanoholes superimposed to the strain relaxation at the step edges are responsible for the improved QDM properties. QDMs are Ga-richer compared to single QDs, consistent with strain- enhanced intermixing. The high optical quality of single QDMs is probed by micro-photoluminescence spectroscopy in samples with QDM densities lower than 108 cm−2.