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

We demonstrate that the presence of charge around a semiconductor quantum dot (QD) strongly affects its optical properties and produces non-resonant coupling to the modes of a microcavity. We first 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 can be suppressed by the application of an electric field, making the QD closer to an ideal two-level system.Comment: 12 pages, 4 figure

Single photonics at telecom wavelengths using nanowire superconducting detectors

Single photonic applications - such as quantum key distribution - rely on the transmission of single photons, and require the ultimate sensitivity that an optical detector can achieve. Single-photon detectors must convert the energy of an optical pulse containing a single photon into a measurable electrical signal. We report on fiber-coupled superconducting single-photon detectors (SSPDs) with specifications that exceed those of avalanche photodiodes (APDs), operating at telecommunication wavelength, in sensitivity, temporal resolution and repetition frequency. The improved performance is demonstrated by measuring the intensity correlation function g(2)(t) of single-photon states at 1300nm produced by single semiconductor quantum dots (QDs).Comment: 7 pages, 5 figures - submitted 12 OCT 200

Enhanced spontaneous emission in a photonic crystal light-emitting diode

We report direct evidence of enhanced spontaneous emission in a photonic crystal (PhC) light-emitting diode. The device consists of p-i-n heterojunction embedded in a suspended membrane, comprising a layer of self-assembled quantum dots. Current is injected laterally from the periphery to the center of the PhC. A well-isolated emission peak at 1300nm from the PhC cavity mode is observed, and the enhancement of the spontaneous emission rate is clearly evidenced by time-resolved electroluminescence measurements, showing that our diode switches off in a time shorter than the bulk radiative and nonradiative lifetimesComment: 10 page

The Gas Sensing Properties of Porphyrins-coated Laterally Grown ZnO Nanorods

AbstractPorphyrins coated ZnO is an interesting material where the exposure to light and gas may cooperate to modulate the respective sensitivities. In this work, the gas sensing properties of porphyrins functionalized laterally grown ZnO nanorods are introduced. The porphyrin layer incompletely coats the semiconductor surface in order to keep both ZnO and porphyrins in contact with analyte. It is known that UV light may prompt the chemical sensitivity of ZnO replacing the high temperature condition. Here we demonstrate that because of the photo-injection of electrons from porphyrin to the ZnO, the same impact could be acquired with visible light

Time-resolved and antibunching experiments on single quantum dots at 1300 nm

We present time integrated and time-resolved photoluminescence (PL) measurements on a single InAs/GaAs quantum dot (QD), embedded in a planar microcavity, emitting in the 1300 nm telecom band. The results of both measurements clearly identify the exciton and biexciton transitions from a single QD. By optimizing the extn. efficiency of the QD PL into the single mode fibers and carefully tuning two InGaAs avalanche photodiodes, we were able to measure the second order correlation function with integration times comparable to those made with silicon based technol. These measurements demonstrate that our single QDs are efficient sources of triggered single photons for quantum key distribution in the O band. [on SciFinder (R)

Log it analysis in the evaluation of the susceptibility of T. cinnabarinus to an acaricide

In order to evaluate the susceptibility of red carmin spider population Tetranvchus cinnabarinus to the commercial product Omethoate (soluble concentrate organic phosphorate), samples were taken in four commercial carnation crops. Susceptibility test were carried out to determine the CL50 in laboratory conditions. Difterence of 1.8 to 3.2 times in the reference population were found. Based upon the level of tolerance to the product the CL50 was determined through 17 generations of inbreeding in absence of applications of the omethoate. From the 81h generation a recovering susceptibility and a significant decrease in the LC50, near LC50 of the reference strain, was demonstrated. The results obtained and the statistical methodology proposed give basic information of the study of susceptibility and management of resistance of T. cinnabarinus to pesticides.Con el fin de evaluar la susceptibilidad al ometoato (concentrado soluble organofosforado) en poblaciones de arañita roja común Tetranichus cinnabarinus, se tomaron muestras de 4 localidades comerciales productoras de clavel. Con las poblaciones de estos cultivos se efectuaron pruebas de susceptibilidad para determinar la concentración letal 50 por ciento en condiciones de laboratorio. En los cultivos estudiados se encontraron diferencias de 1.8 a 3.2 veces en la concentración letal 50 por ciento de T. cinnabarinus al ometoato con relación a la población susceptible de referencia. Con base en el nivel de tolerancia al ometoato, se determinó la variación de la concentración letal 50 por ciento a través de 17 generaciones de autocruzamiento; a partir de la octava generación la población mostró una disminución significativa en la concentración letal 50% tornándose tan susceptible al ometoato como la población susceptible de referencia. La metodología estadística propuesta y los resultados obtenidos proporcionan información básica para el estudio de la susceptibilidad y manejo de la resistencia de T. cinnabarinus a los acaricidas

Controlling the Cassie-to-Wenzel Transition: an Easy Route towards the Realization of Tridimensional Arrays of Biological Objects

In this paper we provide evidence that the Cassie-to-Wenzel transition, despite its detrimental effects on the wetting properties of superhydrophobic surfaces, can be exploited as an effective micro-fabrication strategy to obtain highly ordered arrays of biological objects. To this purpose we fabricated a patterned surface wetted in the Cassie state, where we deposited a droplet containing genomic DNA. We observed that, when the droplet wets the surface in the Cassie state, an array of DNA filaments pinned on the top edges between pillars is formed. Conversely, when the Cassie-to-Wenzel transition occurs, DNA can be pinned at different height between pillars. These results open the way to the realization of tridimensional arrays of biological objects

Enhanced spontaneous emission rate from single InAs quantum dots in a photonic crystal nanocavity at telecom wavelengths

The authors demonstrate coupling at 1.3 micro m between single InAs quantum dots (QDs) and a mode of a two dimensional photonic crystal (PhC) defect cavity with a quality factor of 15 000. By spectrally tuning the cavity mode, they induce coupling with excitonic lines. They perform a time integrated and time-resolved photoluminescence and measure an eightfold increase in the spontaneous emission rate inducing a coupling efficiency of 96%. These measurements indicate the potential of single QDs in PhC cavities as efficient single-photon emitters for fiber-based quantum information processing applications. [on SciFinder (R)