Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication Citation for published version (APA):Zinoni, C., Alloing, B., Li, L., Marsili, F., Fiore, A., Lunghi, L., ... Gol'tsman, G. N. (2007). Single-photon experiments at telecommunication wavelengths using nanowire superconducting detectors. Applied Physics Letters, 91(3), 031106-1/3. [031106]. DOI: 10.1063/1.2752108 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The authors report fiber-coupled superconducting single-photon detectors with specifications that exceed those of avalanche photodiodes, operating at telecommunication wavelength, in sensitivity, temporal resolution, and repetition frequency. The improved performance is demonstrated by measuring the intensity correlation function g ͑2͒ ͑͒ of single-photon states at 1300 nm produced by single semiconductor quantum dots.

We unveil the role of bound-to-continuum photoexcitation of carriers as a relevant process that affects the performance of quantum dot (QD) lasers. We present the response of an InAs/InGaAs QD laser to a sub-band gap pump, showing an unexpected depletion of the emitted photons. We relate this observation with carrier photoexcitation through additional transmission and photocurrent measurements. We provide a theoretical support to the experimental data and highlight the important role of this process in the laser characteristics.The electronic structure of semiconductor quantum dots (QDs) presents dramatic differences from the electronic structure of the bulk material from which they are derived, exhibiting unique properties for their use in lasers and other photonic devices. Besides interband optical transitions commonly used for laser operation, intraband transitions can also occur in QDs and have been applied to QD infrared photodetectors. [1][2][3] For photon energies in the near-infrared, these transitions involve final states high in the continuum and produce an optical loss (corresponding to free-carrier absorption in bulk materials) for the wave propagating in the laser cavity. While in bulk, intraband transitions are forbidden in the first order as they do not conserve momentum, in QDs, the localized nature of the initial bound state makes the transition allowed for any photon energy, similarly to photoionisation in atoms. 4 The absorption cross-section for this process has been calculated 5 to be several orders of magnitude larger than in bulk. It can affect the performance of a QD laser both through the increased optical loss and through the gain reduction resulting from the removal of carriers from the lasing state. Despite its potential significance, to the best of our knowledge, no experimental evidence of this process and of its effect on laser characteristics has been provided. In this paper, we investigate the emission of an InAs/GaAs 1.3 µm QD laser under injection of sub-band gap 1.5 µm, 100 fs pulses, and we find clear evidence of carrier photoexcitation in the strong depletion of laser output. We further confirm this interpretation by directly measuring the pump transmission and induced photocurrent as a function of carrier population in the QDs. The experimental dynamics is well reproduced by a rate equation model, which takes into account the experimental photoexcitation cross-section. This process is then shown to play a role in the static and dynamic characteristics of QD lasers.The QD lasers analyzed were grown by molecular beam epitaxy in the Stranski-Krastanov mode, which has been proved to be a reliable method to provide semiconductor embedded dots. The active layer consists of five layers of self-assembled InAs QDs, covered by 5 nm thick InGaAs capping layers and separated from each other by a 40 nm GaAs active layer. The areal dot density of our lens-shaped QDs is 3 × 10 10 cm -2 . The waveguide was clad by 1.5 µm of AlGaAs, n-doped on the substrate side and p-doped on the t...

We directly investigate, by means of near-field spectroscopy, the spatial distribution of the optical cavity modes of 2D photonic crystal microcavities. Numerical simulations confirm that the photoluminescence maps of quantum dots embedded in the photonic structure qualitatively match the spatial modulation of the electric field intensity. r