Download or read book Contr le de l mission spontan e dans les cristaux photoniques written by Rémy Braive and published by . This book was released on 2008 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: POUR CONTROLER L'EMISSION SPONTANEE, LA SOLUTION QUE NOUS AVONS ETUDIEE UTILISE L'EFFET PURCELL POUR ACCÉLÉRER LA DYNAMIQUE DE L'ÉMISSION SPONTANÉE PRÉFÉRENTIELLEMENT DANS LE MODE LASER. ON APPELLE β LA FRACTION DE L'ÉMISSION SPONTANÉE DANS CE MODE. POUR CELA, IL EST INDISPENSABLE D'AVOIR UNE CAVITÉ AVEC UN FORT Q ET UN FAIBLE V. LES CAVITÉS À CRISTAL PHOTONIQUE PERMETTENT D'OBTENIR SES CARACTÉRISTIQUES EN CHOISISSANT UN DESSIN ADÉQUAT. NOUS AVONS CHOISI LA CAVITÉ À DOUBLE HÉTÉROSTRUCTURE POUR NOTRE ÉTUDE. EN MODIFIANT LA TAILLE DU DÉFAUT DE LA CAVITÉ, NOPUS AVONS PU METTRE EN ÉVIDENCE LA SATURATION DE L'ÉMISSION SPONTANÉE ET L'EFFET LASER. DANS LE SECOND CAS, LA FRACTION β A PU ÊTRE CONTRÔLÉE POUR ATTEINDRE DES VALEURS ENTRE 0,44 ET 0,93. AVEC UNE CAVITÉ PRÉSENTANT UN FACTEUR p DE 0,67, UNE ÉTUDE DE SA RÉPONSE TEMPORELLE À UNE IMPULSION LASER NOUS A PERMIS D'INVESTIGUER LA DYNAMIQUE DE L'EFFET LASEREN FONCTION DE LA PUISSANCE D'EXCITATION. POUR DES PUISSANCES SUPÉRIEURS À CELLE DU SEUIL, LA RÉPONSE DE LA CAVITÉ EST LIMITÉE PAR LE TEMPS DE CAPTURE DES PORTEURS PAR LES BOÎTES QUANTIQUES ET LE TEMPS DE VIE DES PHOTONS DANS LA CAVITÉ. CES TEMPS SONT TOUS DEUX DE L'ORDRE DE 20 PS, CE QUI INDUIT UN PROFIL GAUSSIEN POUR LA RÉPONSE. CES CARACTÉRISTIQUES TEMPORELLES NOUS ONT PERMIS D'OBTENIR UN TAUX DE RÉPÉTITION MAXIMUM AVEC DES MODULATIONS DIRCTES DE 10 GHZ. DANS LE MÊME TEMPS, NOUS AVONS MENÉ UNE ÉTUDE DE L'ÉLARGISSEMENT DE LA RAIE LASER. POUR UNE SIMPLE IMPULSION, LE CHIRP EST LINÉAIRE LORS DE L'IMPULSION AVEC UN FACTEUR DE HENRY DE 3. EN RÉITÉRANT CETTE DÉMARCHE POUR LES MODULATIONS DIRECTES, LE CHIRP EST IDENTIQUE À CELUI OBTENU AVEC UNE IMPULSION SIMPLE.
Download or read book Mat riaux artificiels ing nierie de dispersion des micro ondes l optique written by VANBESIEN Olivier and published by Lavoisier. This book was released on 2012-04-16 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ce livre propose une synthèse des recherches - des concepts jusqu'aux applications - sur les matériaux artificiels, incluant les cristaux photoniques et les métamatériaux. Il expose les enjeux de performance et les défis de fabrication (jusqu'à l'échelle du nanomètre) pour l'exploitation des effets d'ultra-réfraction ou de réfraction négative induits par l'ingénierie généralisée ou localisée de la dispersion sur l'ensemble du spectre électromagnétique (des micro-ondes à l'optique en passant par le térahertz et l'infrarouge). Didactique, Matériaux artificiels analyse les possibilités de l'optique de transformation tels que les mirages optiques, les lentilles parfaites, les tapis magiques et les capes d'invisibilité. Présentés comme potentiels précurseurs de nouveaux systèmes de contrôle de la propagation des ondes et/ou d'imagerie pour les domaines des télécommunications, de la biologie ou de la médecine, ils permettent d'identifier les principaux verrous théoriques et technologiques actuels.
Download or read book Propagation et mission dans des guides multimodes cristaux photoniques bidimensionnels written by Emilie Schwoob-Viasnoff and published by . This book was released on 2004 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: The physics of a Fabry Perot cavity with grating mirrors, substantiated here by a multimode 2D photonic crystal waveguide, is investigated from a mainly experimental point of view. Applications in the field of optical telecommunications around 1.55 [mu]m, as well as more fundamental issues are addressed. The guide walls consist of a periodic grating of air holes etched through a InP-based heterostructure. They are completely reflecting within the photonic band gap for any wave impinging within the periodicity plane. The periodicity along the guide couples through Bragg diffraction guided modes, with "ordinary" group velocity, with very slow modes, analogous to resonant modes. The new feature about this coupling is that it occurs only within small frequency and wavevector windows, remaining silent elsewhere. This coupling is firstly used to design a wavelength multiplexer/demultiplexer, extracting, laterally with respect to the guide direction and selectively, all or part of the guided optical signal. The following and more fundamental parts of this manuscript investigate the potential impact of the spectral regions nearby these coupling windows in order to control the spontaneous emission of photons within these confining and diffractive structures. We present a sinking experimental spontaneous emission enhancement, related to a peaked photon density of states. The last part deals with a measurement of the modal gain spectrum: the consequence of the slowing of a guided mode around the coupling window onto the optical amplification of a propagating signal is discussed.
Download or read book Optique non lin aire dans les cristaux photoniques en semiconducteur III V written by Fabrice Raineri and published by . This book was released on 2004 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: Depuis la proposition initiale en 1987 par E. Yablonovitch et S. John du concept de cristaux photoniques, un grand nombre d'études ont démontré que ces structures périodiques permettent de contrôler de façon efficace la propagation de la lumière. La recherche concernant les cristaux photoniques traite aujourd'hui des aspects fondamentaux comme le contrôle de l'émission spontanée mais aussi des sujets plus applicatifs comme les lasers à faible seuil et les circuits photoniques pour l'optique intégrée. La principale raison de cette activité intense est que, grâce à la structuration de la matière à l'échelle de la longueur d'onde de la lumière, il est possible de réaliser une véritable ingénierie des propriétés dispersives de ces objets : la propagation de la lumière peut être ainsi empêchée sur de grandes plages de fréquences (gap photonique), la vitesse de phase et la vitesse de groupe de la lumière peuvent aussi être contrôlées. Ceci peut mener à la localisation du champ électromagnétique et, en conséquence, à une exaltation des interactions entre la lumière et la matière.Dans cette thèse, nous nous sommes intéressés d'une part à la conception et à la fabrication de cristaux photoniques unidimensionnels et bidimensionnels en AlGaAs pour réaliser des convertisseurs de fréquence ultracourts pour l'optique intégrée. D'autre part, nous montrons qu'en utilisant de façon avantageuse les fortes non linéarités du troisième ordre des semiconducteurs III-V dans les cristaux photoniques bidimensionnels, on peut obtenir de l'effet laser, de l'accordabilité spectrale, de la commutation ultra rapique et de l'amplification.
Download or read book Controle de l mission de nanofils semiconducteurs par couplage un cristal photonique vers des nanolasers int grables written by Christophe Wilhelm and published by . This book was released on 2015 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book CRISTAUX PHOTONIQUES BIDIMENSIONNELS POUR LE PROCHE INFRAROUGE written by Dominique Labilloy and published by . This book was released on 1999 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: LES MATERIAUX A BANDE INTERDITE DE PHOTONS (BIPS) OU CRISTAUX PHOTONIQUES, SONT DES STRUCTURES, GENERALEMENT ARTIFICIELLES, DONT L'INDICE DIELECTRIQUE VARIE PERIODIQUEMENT. LORSQUE LE CONTRASTE D'INDICE EST FORT, ON PREDIT THEORIQUEMENT QU'ELLES DOIVENT EMPECHER LA PROPAGATION DE LA LUMIERE DANS TOUTES LES DIRECTIONS EN CREANT DES PLAGES SPECTRALES (LES BANDES INTERDITES) A DENSITE D'ETAT DE PHOTONS NULLE. NOUS AVONS ETUDIE LE COMPORTEMENT OPTIQUE DE CRISTAUX PHOTONIQUES BIDIMENSIONNELS GRAVES DANS DES HETEROSTRUCTURES SEMICONDUCTRICES GUIDANTES. L'ORIGINALITE CONSISTE A UTILISER LA PHOTOLUMINESCENCE DE BOITES OU PUITS QUANTIQUES COMME SOURCE LUMINEUSE INTERNE. CETTE TECHNIQUE A PERMIS D'EFFECTUER UNE CARACTERISATION COMPLETE DE CES OBJETS EN MESURANT QUANTITATIVEMENT LES COEFFICIENTS DE TRANSMISSION ET DE REFLEXION AINSI QUE LES PROPRIETES DE DIFFRACTION. AUX ZONES DE FAIBLE TRANSMISSION CORRESPONDENT DE FORTS COEFFICIENTS DE REFLEXION OU DE DIFFRACTION, CE QUI INDIQUE QUE L'ONDE RESTE GUIDEE LORS DE L'INTERACTION AVEC LES CRISTAUX ET CONFIRME LEUR FORT POTENTIEL POUR L'OPTIQUE INTEGREE. NOUS AVONS UTILISE CES REFLECTEURS POUR REALISER DES CAVITES, D'ABORD UNIDIMENSIONNELLES, QUI MONTRENT UNE BONNE FINESSE EN TRANSMISSION, CONFIRMANT QUE LES PERTES HORS DU PLAN DU GUIDE SONT FAIBLES. NOUS AVONS ENSUITE ETUDIE DES CAVITES TRIDIMENSIONNELLES DE FAIBLE VOLUME (5 M#3), SONDEES CETTE FOIS-CI A L'AIDE D'EMETTEURS INTERNES A LA CAVITE. L'APPARITION DE PICS ETROITS MONTRE QUE L'EFFET DE CONFINEMENT EST IMPORTANT ET LAISSE PRESAGER DE REELLES POTENTIALITES DE MODIFICATION DE L'EMISSION SPONTANEE.
Download or read book COLOQ 6 written by Alain Aspect and published by . This book was released on 2000 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Journal de physique written by and published by . This book was released on 2006 with total page 772 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spectral Photon Counting Computed Tomography written by Katsuyuki Taguchi and published by CRC Press. This book was released on 2020-07-14 with total page 446 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spectral, Photon Counting Computed Tomography is a comprehensive cover of the latest developments in the most prevalent imaging modality (x-ray computed tomography (CT)) in its latest incarnation: Spectral, Dual-Energy, and Photon Counting CT. Disadvantages of the conventional single-energy technique used by CT technology are that different materials cannot be distinguished and that the noise is larger. To address these problems, a novel spectral CT concept has been proposed. Spectral Dual-Energy CT (DE-CT) acquires two sets of spectral data, and Spectral Photon Counting CT (PC-CT) detects energy of x-ray photons to reveal additional material information of objects by using novel energy-sensitive, photon-counting detectors. The K-edge imaging may be a gateway for functional or molecular CT. The book covers detectors and electronics, image reconstruction methods, image quality assessments, a simulation tool, nanoparticle contrast agents, and clinical applications for spectral CT.
Download or read book Oxidative Stress and Redox Regulation written by Ursula Jakob and published by Springer Science & Business Media. This book was released on 2013-03-15 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many physiological conditions such as host defense or aging and pathological conditions such as neurodegenerative diseases, and diabetes are associated with the accumulation of high levels of reactive oxygen species and reactive nitrogen species. This generates a condition called oxidative stress. Low levels of reactive oxygen species, however, which are continuously produced during aerobic metabolism, function as important signaling molecules, setting the metabolic pace of cells and regulating processes ranging from gene expression to apoptosis. For this book we would like to recruit the experts in the field of redox chemistry, bioinformatics and proteomics, redox signaling and oxidative stress biology to discuss how organisms achieve the appropriate redox balance, the mechanisms that lead to oxidative stress conditions and the physiological consequences that contribute to aging and disease.
Download or read book Quantum Communications and Cryptography written by Alexander V. Sergienko and published by CRC Press. This book was released on 2018-10-03 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: All current methods of secure communication such as public-key cryptography can eventually be broken by faster computing. At the interface of physics and computer science lies a powerful solution for secure communications: quantum cryptography. Because eavesdropping changes the physical nature of the information, users in a quantum exchange can easily detect eavesdroppers. This allows for totally secure random key distribution, a central requirement for use of the one-time pad. Since the one-time pad is theoretically proven to be undecipherable, quantum cryptography is the key to perfect secrecy. Quantum Communications and Cryptography is the first comprehensive review of the past, present, and potential developments in this dynamic field. Leading expert contributors from around the world discuss the scientific foundations, experimental and theoretical developments, and cutting-edge technical and engineering advances in quantum communications and cryptography. The book describes the engineering principles and practical implementations in a real-world metropolitan network as well as physical principles and experimental results of such technologies as entanglement swapping and quantum teleportation. It also offers the first detailed treatment of quantum information processing with continuous variables. Technologies include both free-space and fiber-based communications systems along with the necessary protocols and information processing approaches. Bridging the gap between physics and engineering, Quantum Communications and Cryptography supplies a springboard for further developments and breakthroughs in this rapidly growing area.
Download or read book Organic Solid State Lasers written by Sébastien Forget and published by Springer. This book was released on 2013-07-03 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic lasers are broadly tunable coherent sources, potentially compact, convenient and manufactured at low-costs. Appeared in the mid 60’s as solid-state alternatives for liquid dye lasers, they recently gained a new dimension after the demonstration of organic semiconductor lasers in the 90's. More recently, new perspectives appeared at the nanoscale, with organic polariton and surface plasmon lasers. After a brief reminder to laser physics, a first chapter exposes what makes organic solid-state organic lasers specific. The laser architectures used in organic lasers are then reviewed, with a state-of-the-art review of the performances of devices with regard to output power, threshold, lifetime, beam quality etc. A survey of the recent trends in the field is given, highlighting the latest developments with a special focus on the challenges remaining for achieving direct electrical pumping of organic semiconductor lasers. A last chapter covers the applications of organic solid-state lasers.
Download or read book Experimental Chaos written by Stefano Boccaletti and published by A I P Press. This book was released on 2004-12-14 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 8th Experimental Chaos Conference again demonstrated the broad spectrum of areas where nonlinear dynamics plays an important role, such as circuits, hydrodynamics, optics, chemistry, fracture dynamics, neuroscience, and cognitive science. Additional contributions outline the trends for development and application of concepts and techniques of nonlinear dynamics.
Download or read book Laser 50 Years Of Discoveries written by Fabien Bretenaker and published by World Scientific. This book was released on 2014-10-27 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unique book provides an overview of the principle and applications of lasers enriched with numerous illustrations.Being over fifty years old, lasers continue to amaze us. Their performance characteristics are constantly reaching new limits, and the scope of their applications continues to expand. Yet, it took years of effort by teams of physicists to transform the fundamental notions of Einstein into the first experimental beam of laser light. And history is still going on as fundamental research is now triggered by its remarkable properties.This book addresses every aspects of laser light, from its fundamental principles to its industrial applications, at a level particularly suited for high school teachers, students, and anybody curious about science and technology.
Download or read book Electrons in Molecules written by Jean-Pierre Launay and published by Oxford University Press, USA. This book was released on 2014 with total page 511 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this book is to provide the reader with essential keys to a unified understanding of the rapidly expanding field of molecular materials and devices: electronic structures and bonding, magnetic, electrical and photo-physical properties, and the mastering of electrons in molecular electronics. Chemists will discover how basic quantum concepts allow us to understand the relations between structures, electronic structures, and properties of molecular entities and assemblies, and to design new molecules and materials. Physicists and engineers will realize how the molecular world fits in with their need for systems flexible enough to check theories or provide original solutions to exciting new scientific and technological challenges. The non-specialist will find out how molecules behave in electronics at the most minute, sub-nanosize level. The comprehensive overview provided in this book is unique and will benefit undergraduate and graduate students in chemistry, materials science, and engineering, as well as researchers wanting a simple introduction to the world of molecular materials.
Download or read book Physical Properties of Amorphous Materials written by David Adler and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Institute for Amorphous Studies was founded in 1982 as the international center for the investigation of amorphous mate rials. It has since played an important role in promoting the und er standing of disordered matter in general. An Institute lecture series on "Fundamentals of Amorphous Materials and Devices" was held during 1982-83 with distinguished speakers from universities and industry. These events were free and open to the public ,and were attended by many representatives of the scientific community. The lectures themselves were highly successful inasmuch as they provided not only formal instruction but also an opportunity for vigorous and stimulating debate. That last element could not be captured within the pages of a book I but the lectures concentrated on the latest advances in the field I which is why their essential contents are he re reproduced in collective form. Together they constitute an interdisciplinary status report of the field. The speakers brought many different viewpoints and a variety of back ground experiences io bear on the problems involved I but though language and conventions vary I the essential unity of the concerns is very clear I as indeed are the ultimate benefits of the many-sided approach.
Download or read book Transmission Electron Microscopy in Micro nanoelectronics written by Alain Claverie and published by John Wiley & Sons. This book was released on 2013-01-29 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: Today, the availability of bright and highly coherent electron sources and sensitive detectors has radically changed the type and quality of the information which can be obtained by transmission electron microscopy (TEM). TEMs are now present in large numbers not only in academia, but also in industrial research centers and fabs. This book presents in a simple and practical way the new quantitative techniques based on TEM which have recently been invented or developed to address most of the main challenging issues scientists and process engineers have to face to develop or optimize semiconductor layers and devices. Several of these techniques are based on electron holography; others take advantage of the possibility of focusing intense beams within nanoprobes. Strain measurements and mappings, dopant activation and segregation, interfacial reactions at the nanoscale, defect identification and specimen preparation by FIB are among the topics presented in this book. After a brief presentation of the underlying theory, each technique is illustrated through examples from the lab or fab.
