B Alloing

Controlling the charge environment of single quantum dots in a photonic-crystal cavity

We demonstrate that the presence of charges around a semiconductor quantum dot (QD) strongly affects its optical properties and produces nonresonant coupling to the modes of a microcavity. We show that, besides (multi)exciton lines, a QD generates a spectrally broad emission which efficiently couples to cavity modes. Its temporal dynamics shows that it is related to the Coulomb interaction between the QD (multi)excitons and carriers in the adjacent wetting layer. This mechanism is suppressed by the application of an electric field, making the QD closer to an ideal two-level system.

Telecom-wavelength single-photon sources for quantum communications

This paper describes the progress towards the realization of efficient single-photon sources based on semiconductor quantum dots (QDs), for application in quantum key distribution and, more generally, quantum communications. We describe the epitaxial growth of QD arrays with low areal density and emitting in the telecom wavelength range, the nanofabrication of single-QD structures and devices, and their optical and electro-optical characterization. The potential for integration with monolithic microcavities is also discussed.

Scanning near-field optical microscopy of quantum dots in photonic crystal cavities

Nanophotonic devices are of major interest for research and future quantum communication applications. Due to their nanometer feature size the resolution limit of far-field microscopy poses a limitation on the characterization of their optical properties. A method to overcome the resolution limit is the Scanning Near-Field Optical Microscope (SNOM). By approaching a fiber tip into the close vicinity of the sample the optical emission in the near-field regime is collected. This way of collecting the light is not affected by the diffraction limit. We employ a low temperature SNOM to investigate the photoluminescence of InAs QDs emitting at 1300nm wavelength embedded in photonic crystal cavities. At each location of an image scan the tip is stopped and a spectrum is acquired. We then plot maps of the photoluminescence for each wavelength. With this instrument it is now possible to directly observe the coupling of QDs to photonic crystal cavities both spectrally and spatially. We show first results of photoluminescence mapping of InAs QDs in photonic crystal cavities.

Single-photonics at telecom wavelengths using nanowire superconducting single photon detectors

Novel single-photon detectors based on NbN superconducting nanostructures promise orders-of-magnitude improvement over InGaAs APDs. We demonstrate this improved performance for the first time by measuring the g(2)(¿) on single photon states produced by a quantum dot at telecom wavelength.

Origin of the non-resonant quantum dot-cavity coupling

Time-resolved experiments are performed on single quantum dots in bulk material and photonic crystal diodes. These studies reveal that the cavity mode can be pumped by a broad emission originating from the presence of carriers in the wetting layer.

Electrical injection of a photonic crystal nanocavity

The possibility of electrical pumping of a single QD and the integration of such a device in an opto-electronic circuit would be a fundamental step towards achieving an ldquoon demandrdquo single photon source. In this paper we describe the fabrication process and preliminary results of a Light Emitting Diode (LED) integrated with a photonic crystal (PhC) nanocavity on a GaAs membrane. We demonstrate effective electric pumping of the QDs embedded into the membrane by contacting the doped layers (p and n) of the thin membrane, and the excitation of cavity modes of the PhC nanocavity fabricated on it at telecom wavelength.

Coupling of single InAs quantum dots at 1.3μm to a photonic crystal defect cavity mode

We show coupling between single 1.3 μm InAs quantum dots (QDs) and photonic crystal nanocavities with quality factors up to 16 500. We demonstrate increased spontaneous emission rate for the first time in telecommunication wavelengths QDs.

Control of the Spontaneous Emission of Single InAs Quantum Dots at 1.3μm in Point-Defect Photonic Crystal Nanocavities

The coupling between single 1.3 μm InAs quantum dots (QDs) and photonic crystal nanocavities with quality factors Q up to 15000 is showed. In this condition the Purcell effect (increased spontaneous emission rate) is observed for the first time at these wavelengths. This result is an important step for the development of semiconductor based single photon sources at telecom wavelength, a fundamental need for application like quantum cryptography and quantum computing.

Enhanced spontaneous emission from InAs/GaAs quantum dots in pillar microcavities emitting at telecom wavelengths

Optical properties of InAs/GaAs quantum dots in micropillar cavities emitting at 1.3 microm are studied by time-resolved microphotoluminescence. The Purcell effect is observed with an enhancement of the decay rate by a factor of two for quantum dots in resonance with the cavity mode.

Telecom-Wavelength Single-Photon Sources from Quantum Dots in Microcavities

We have developed solid-state single-photon sources based on single InAs quantum dots emitting at 1300 nm. We report antibunching experiment and electroluminescence measurements, showing that our system can be used as an efficient single photon source under optical and electrical pumping