C Monat

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.

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.

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

Nanoscale single quantum dot devices at 1300 nm

We describe the realization and characterization of nanoscale light emitters comprising one or few semiconductor quantum dots (QDs) in the active region. These devices are intended for use as single-photon sources in fiber-based quantum cryptography systems. The epitaxial growth of low-density QDs emitting at 1300 nm is described, and emission from single QDs is demonstrated through micro-photoluminescence measurements. The realization of QD light-emitting diodes (LEDs) having a submicrometer active area is reported, based on oxidized current apertures. Finally, the integration of nanoscale current injection with high-quality factor optical cavities is described, in view of obtaining efficient single-photon LEDs.

Technology CAD based design of semiconductor optical microcavities for single photon emitters

Optical microcavities that contain single quantum dots have promising applications in quantum cryptography as sources of single photons. The realisation of efficient devices relies on the ability to fabricate electrically-pumped, high Q factor (Q>2000), wavelength-sized microcavities. In this work two approaches-oxide confined and micropillar structures-are compared by optical simulation. The modification of the spontaneous emission-Purcell factor and emission coupling efficiency-in such devices is treated semiclassically here, assuming the weak coupling regime. Hence, the spontaneous emission rate and direction may be computed using the effective mode volume, resonant wavelength, and quality factor of the optical modes in the microcavity. In the context of this work, the optical modes of rotationally symmetric microcavities are determined by solving Maxwells vectorial wave equation in the frequency domain employing vectorial finite elements, subject to an open boundary, taking into account diffraction and radiation of electromagnetic waves. Consequently, the spontaneous emission properties of realistic microcavities without any restrictions regarding structure and size may be investigated. The optical mode solver is first calibrated with measured electroluminescence spectra of an oxide confined microcavity structure with oxide diameters ranging from 2.4 um to 0.7 um. Excellent agreement is achieved between measurements and simulations, which assures the predictive capability of the optical mode solver. For oxide confinements with diameters smaller than 1 um strong degradation of the Q factor and, hence, the Purcell factor is observed. Excessive diffraction losses are identified as the main cause of this effect in the present design. Furthermore, the advantages of micropillar structures with respect to this issue are demonstrated.