Les exigences de plus en plus élevés concernant la qualité et propriétés de couches minces ont soutenu le développement de nouveaux procédés de pulvérisation. Ainsi, la décharge magnétron conventionnelle en courant continu, une des sources d’atomes la plus utilisée pour le dépôt de couches minces, a été améliorée par le couplage avec une décharge additionnelle de radio fréquence pour obtenir le nouveau procédé RF-IPVD (Radio Frequency-Ionized Physical Vapour Deposition). Ce procédé permet de générer un degré d’ionisation supérieur à celui dans la décharge magnétron classique, nécessaire pour contrôler les propriétés des couches minces. Un procédé alternatif pour augmenter d’avantage l’ionisation consiste à appliquer des impulsions haute puissance sur la cathode HPPMS (High Power Pulsed Magnetron Sputtering), pour des durés courtes de l’ordre de ųs ou dizaines de ųs. L’étude menée porte sur les phénomènes de pulvérisation et de transport des espèces du métal dans ces trois versions de la décharge magnétron par les moyens de spectroscopie laser à l’aide des diodes laser accordables. Le développement récent de ces diodes nous a permis de sonder les niveaux fondamentaux du Titane et de l’Aluminium, et de caractériser la dépendance spatiale de la densité et température ainsi que la fonction de distribution en vitesse de ces atomes. L’effet des paramètres clés, comme l’intensité du courant et la pression du gaz, est étudie et décrit pour la décharge magnétron conventionnelle. La distribution spatiale et angulaire de la fonction de distribution en vitesses a été mesurée dans la région devant la cible magnétron, afin de caractériser les flux du métal et leur comportement dans le volume de la décharge. L’étude sur les atomes du métal dans le procédé RF-IPVD est concentrée sur l’effet de la décharge additionnelle sur le dépeuplement du niveau fondamental. Une efficacité plus grande des processus d’ionisation est trouvée à plus haute pression et plus haute puissance RF injecté. On a montré aussi que les atomes affectés par les processus d’ionisation sont ceux thermalisées, tandis que la distribution de atomes rapides n’est quasiment pas affectés par la décharge additionnelle.Le diagnostic de la décharge pulsée a nécessité le développement d’une nouvelle procédure expérimentale, capable de suivre l’évolution de la densité et de la température des espèces neutres avec une résolution de l’ordre de la ųs. Cette procédure nous a servi pour décrire l’évolution spatio-temporel des atomes du métal (Ti et Al) et les atomes métastables d’Ar. Ces études offrent une vue globale sur le transport de atomes pulvérisés pendant la post décharge, ainsi qu’une description du fonctionnement de la décharge pulsé via la création des métastables d’Argon. / The higher requirements on the thin films quality have supported the development of new sputtering techniques. Thus, the conventional DC magnetron discharge, one of the most widely used source of atoms for thin film deposition, has been improved by the addition of an auxiliary radio frequency discharge - new technique called RF-IPVD (Radio Frequency -Ionized Physical Vapor Deposition). This technique highly increases the ionization degree compared to conventional magnetron discharge, which is necessary for a better control of the thin films properties. An alternative method to increase the ionization is based on the use of high power pulses on the cathode, HPPMS (High Power Pulsed Magnetron Sputtering), for short periods of time ranging from ųs to tens of ųs.The present study focuses on the sputtering phenomena and the transport of metal sputtered species in these three versions of the magnetron discharge, by means of laser spectroscopy using tunable laser diodes. The recent developments of these diodes have allowed to probe the fundamental levels of titanium and aluminum, and to characterize the spatial dependency of the density and temperature as well as the velocity distribution functions of these atoms. The effect of key discharge parameters, such as current intensity and gas pressure, is studied and described for the conventional magnetron discharge. The spatial and angular velocity distribution functions were measured in front of the magnetron target, in order to characterize the metal fluxes and their behavior in the discharge volume.The study on the metal atoms in the RF-IPVD process is focused on the effect of the additional discharge on the depopulation of the ground state level. Higher ionization efficiency is found at relatively high pressure and it increases with the injected RF power. It was also showed that the thermalized atoms are the ones involved in the ionization process, while the distribution of fast atoms is almost unaffected by the additional discharge.The diagnostics of the HPPMS discharge required the development of a novel experimental procedure, able to monitor the density and temperature of neutral species with a time resolution of ųs. This procedure was used to describe the spatiotemporal evolution of metal atoms (Ti and Al) and Ar metastable atoms. These studies provide an overview on the transport of sputtered atoms during the afterglow, and a description of the pulsed discharge operation, via the creation of metastable argon atoms.

This thesis documents the optimized design of a touch screen using infrared technology as a three dimensional problem. The framework is fundamentally built on laser diode technology and introduces mirrors for signal reflection. The rising popularity of touch screens are credited to the naturally intuitive control of display interfaces, extensive data presentation, and the improved manufacturing process of various touch screen implementations. Considering the demands on touch screen technology, the design for a large scaled touch panel is inevitable, and signal reduction techniques become a necessity to facilitate signal processing and accurate touch detection. The developed research model seeks to capture realistic touch screen design limitations to create a deploy-able configuration. The motivation of the problem stems from the significant reduction of representation achieved by combinatorial group theory. The research model is of difficulty NP-complete. Additional exclusive-or functions for uniqueness, strengthening model search space, symmetry eliminating constraints, and implementation constraints are incorporated for enhanced performance. The computational results and analysis of objectives, valuing the emphasis on diodes and layers are evaluated. The evaluation of trade-off between diodes and layers is also investigated.

A cost-effective 25 Gb/s directly-modulated transmitter optical sub-assembly (TOSA) packaging solutions by transistor outline (TO)-Can materials and processes were proposed and demonstrated. The purpose of this dissertation is to develop a high bandwidth TO-Can header for high-speed laser module, to verify a method, to propose a three-version of 25 Gb/s TO-Can laser module packaging, and to analyze in the frequency-domain and time-domain, and to experimentally demonstrate a 25 Gb/s TOSA. Usually, the transmission bandwidth of a conventional TO-Can laser module is limited below 10 GHz. To overcome this limitation and figure out the solution, firstly, the geometric structure of a conventional TO-56 header was analyzed by using transmission line models and electrical characteristics of the TO-56 header through a three-dimensional electromagnetism full-wave simulation software. The simulated results were in good agreement with the measured results and verify the applicability. Furthermore, we found that the 3-dB bandwidth of a conventional TO-56 header was limited at 16.7GHz. In this study, the first version of TO-Can header V1 was proposed to overcome the problem of the discontinuous impedance. By applying the TO-Can header V1, a TO-Can laser module package was proposed. The electrical characteristics parameters of the TO-Can header V1 were extracted and combined with small-signal equivalent circuit models of laser diode to simulate the electrical characteristics of the entire TO-Can laser module by the circuit simulation tool. Since bent inside feed-leads and two-step coaxial feed-through holes of the TO-Can header V1 were difficult to achieve in our laboratory equipments, the second version of TO-Can header V2 was proposed and verified experimentally. A 25 Gb/s TO-Can laser module with a matching resistor by adopting the TO-Can header V2 was proposed. The simulated results of this solution by considering with bonding-wires showed that the transmission bandwidth and eye diagram could achieve requirements of 25 Gb/s transmissions. Finally, the third version of 25 Gb/s TO-Can laser module adopted the TO-Can header V2 and an AlN submount of L-shaped microstrip line was proposed, fabricated, and measured. A DFB LD chip with a 3-dB bandwidth of 21.2 GHz was modeled and used in the simulation and the fabrication. Due to the parasitic effect induced by bonding-wires and die-bonding structure, the variation of high frequency performance of the laser module was simulated comprehensively. By referring to the proposed structure, a TOSA was fabricated by a conventional TO-Can and TOSA fabrication equipments and processes. The measured 3-dB bandwidth of the TOSA was 18.7 GHz. A clear eye diagrams of 25 Gb/s and BER testing for BTB and SMF transmission were obtained. This cost-effective solution of the TOSA is compatible with existing automatic TO-Can process lines and can be fabricated massively. Therefore, the results of this study of proposed TOSA can be applied in the next generation networks of 100GBASE-LR4, OTU4, and 32GFC. The presented simulation and verified technique may provide sufficient estimation and step-by-step analysis to assist the high-speed and high-density optical communication applications and various product developments in the future.

This dissertation describes the development of III-nitride (III-N) bipolar devices for optoelectronic and electronic applications. Research mainly involves device design, fabrication process development, and device characterization for Geiger-mode gallium nitride (GaN) deep-UV (DUV) p-i-n avalanche photodiodes (APDs), indium gallium nitride (InGaN)/GaN-based violet/blue laser diodes (LDs), and GaN/InGaN-based npn radio-frequency (RF) double-heterojunction bipolar transistors (DHBTs). All the epitaxial materials of these devices were grown in the Advanced Materials and Devices Group (AMDG) led by Prof. Russell D. Dupuis at the Georgia Institute of Technology using the metalorganic chemical vapor deposition (MOCVD) technique. Geiger-mode GaN p-i-n APDs have important applications in DUV and UV single-photon detections. In the fabrication of GaN p-i-n APDs, the major technical challenge is the sidewall leakage current. To address this issue, two surface leakage reduction schemes have been developed: a wet-etching surface treatment technique to recover the dry-etching-induced surface damage, and a ledged structure to form a surface depletion layer to partially passivate the sidewall. The first Geiger-mode DUV GaN p-i-n APD on a free-standing (FS) c-plane GaN substrate has been demonstrated. InGaN/GaN-based violet/blue/green LDs are the coherent light sources for high-density optical storage systems and the next-generation full-color LD display systems. The design of InGaN/GaN LDs has several challenges, such as the quantum-confined stark effect (QCSE), the efficiency droop issue, and the optical confinement design optimization. In this dissertation, a step-graded electron-blocking layer (EBL) is studied to address the efficiency droop issue. Enhanced internal quantum efficiency (ɳi) has been observed on 420-nm InGaN/GaN-based LDs. Moreover, an InGaN waveguide design is implemented, and the continuous-wave (CW)-mode operation on 460-nm InGaN/GaN-based LDs is achieved at room temperature (RT). III-N HBTs are promising devices for the next-generation RF and power electronics because of their advantages of high breakdown voltages, high power handling capability, and high-temperature and harsh-environment operation stability. One of the major technical challenges to fabricate high-performance RF III-N HBTs is to suppress the base surface recombination current on the extrinsic base region. The wet-etching surface treatment has also been employed to lower the surface recombination current. As a result, a record small-signal current gain (hfe) > 100 is achieved on GaN/InGaN-based npn DHBTs on sapphire substrates. A cut-off frequency (fT) > 5.3 GHz and a maximum oscillation frequency (fmax) > 1.3 GHz are also demonstrated for the first time. Furthermore, A FS c-plane GaN substrate with low epitaxial defect density and good thermal dissipation ability is used for reduced base bulk recombination current. The hfe > 115, collector current density (JC) > 141 kA/cm², and power density > 3.05 MW/cm² are achieved at RT, which are all the highest values reported ever on III-N HBTs.

This thesis documents the optimized design of a touch screen using infrared technology as a three dimensional problem. The framework is fundamentally built on laser diode technology and introduces mirrors for signal reflection. The rising popularity of touch screens are credited to the naturally intuitive control of display interfaces, extensive data presentation, and the improved manufacturing process of various touch screen implementations. Considering the demands on touch screen technology, the design for a large scaled touch panel is inevitable, and signal reduction techniques become a necessity to facilitate signal processing and accurate touch detection. The developed research model seeks to capture realistic touch screen design limitations to create a deploy-able configuration. The motivation of the problem stems from the significant reduction of representation achieved by combinatorial group theory. The research model is of difficulty NP-complete. Additional exclusive-or functions for uniqueness, strengthening model search space, symmetry eliminating constraints, and implementation constraints are incorporated for enhanced performance. The computational results and analysis of objectives, valuing the emphasis on diodes and layers are evaluated. The evaluation of trade-off between diodes and layers is also investigated.

Made available in DSpace on 2016-12-12T20:15:53Z (GMT). No. of bitstreams: 1 parte1.pdf: 63647 bytes, checksum: f2fd5c831fcfe5e4d704fd18bec2cc27 (MD5) Previous issue date: 2010-03-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Laser cooling in high magnetic fields, presents a series of difficulties due to inhomogeneous broadening of the frequency due to Zeeman Effect. In the first part of this work we investigate the laser cooling of Li by a Monte Carlo simulation, the 2S(1/2)-> 2P(3/2) transition at 670.96 nm in a magnetic trap under the characteristics of trap operating at the LASER laboratory of the Institute of Physics, UFRJ. In the second part, we built a diode laser with extended Littrow cavity emitting in 972 nm using the configuration of extended cavity Littrow. The purpose of this laser is, after a double frequency doubling, to use it to study the hydrogen atom in the transition 1S -> 2S at 243 nm. / O resfriamento a laser em altos campos magnéticos, apresenta uma série de dificuldades devido ao alargamento inomogêneo da transição causado pelo efeito Zeeman. Na primeira parte desse trabalho investigamos o resfriamento a laser de Lítio através de uma simulação de Monte Carlo, na transição 2S1/2 -> 2P3/2 em 670.96 nm, em uma armadilha magnética com as características da armadilha em funcionamento no laboratório LASER do instituto de Física da UFRJ. Na segunda parte, foi construído um laser de diodo em cavidade estendida emitindo em 972 nm utilizando a configuração de Cavidade Estendida de Littrow. O propósito desse laser e após um duplo dobramento de freqüência, utilizá-lo para estudo do átomo de Hidrogênio na transição 1S -> 2S em 243 nm.

IntroductionLes cicatrices chéloïdes (CC) sont des pathologies de la cicatrisation cutanée entraînant des gênes fonctionnelles et esthétiques souvent invalidantes. Elles sont liées à un excès de fabrication et une désorganisation du collagène lié en parti à un dérèglement du TGFβ. Les lasers thermiques permettent d'améliorer la cicatrisation par le biais d'une modification de la réponse inflammatoire. En effet, une élévation de la température entre 45 et 53°C entraine une hyperexpression des HSP 70, responsables d’une modification de l’expression du TGFβ. Le laser diode 810nm a déjà prouvé son efficacité mais il est contre indiqué chez les sujets de phototypes foncés qui sont les plus à risque de développer des CC. L'objectif de ce travail était d'évaluer l'effet d’un laser thermique sur les cicatrices chéloïdes chez l’animal et dans le cadre d’une étude clinique.Détermination des paramètres su laserDes études sur des explants de peau, puis sur des sujets volontaires sains ont permis de montrer que la longueur d’onde 1210 nm était la plus adaptée dans cette indication car elle est peu absorbée par la mélanine. Le choix des paramètres du laser ont également été déterminés afin d’obtenir une élévation contrôlée de la température cutanée. En théorie, un tir de laser diode 1210 nm, 5.1W/cm² pendant 10 secondes permet d’élever la température jusqu’à 53°C.Mise au point d’un modèle animal de CCIl n’existe pas de modèle animal de CC permettant d’étudier l’effet d’un laser. Nous avons donc mis au point un modèle pour le besoin de l’étude. Des fragments de CC humaines comprenant le derme et l’épiderme ont été greffés chez 40 souris nudes. Une évaluation clinique et histologique a permis de confirmer la bonne intégration du greffon et la persistance de son caractère chéloïde pendant 4 mois.Etude du laser diode 1210nm chez un modèle animal de CCUne étude du laser 1210 nm a été réalisée sur notre modèle animal. Il a été réalisé des tirs de laser directement sur les greffons et des évaluations cliniques et histologiques ont permis de montrer l’absence d’effet indésirable. La mesure de la température cutanée au moment du tir de laser était de 45°C en moyenne.Etude du laser diode 1210nm après excision intra chéloïdienne : étude cliniqueParallèlement à l’étude animale, il a été réalisé une étude pilote visant à évaluer la faisabilité et la sécurité d’un protocole de traitement des cicatrices chéloïdes utilisant le laser diode 1210nm. Il était réalisé une excision intra cicatricielle, puis la suture était irradiée par le laser 1210nm pendant environs 10 secondes. 20 patients ont été inclus dans l’étude. L’objectif de suivi était de 2 ans, mais l’étude est toujours en cours. Jusqu’à présent, il n’a été noté aucun effet délétère du laser. 8 patients ont bénéficié d’injections de corticoïdes en raison de récidive de la chéloïde à 6 mois.ConclusionCe travail à permis de mettre au point un modèle animal original de cicatrice chéloïde permettant pour la première fois l’étude des lasers in vivo. L’utilisation du laser 1210nm, 5.1W/cm2, pendant 10 secondes à entrainé une élévation de la température cutanée jusqu’à 45°C en moyenne sans aucun effet délétère sur la CC chez la souris. L’utilisation du laser thermique diode 1210 nm après une résection intra chéloïdienne n’a montré aucun signe de toxicité chez l’homme. La température cutanée était de 48°C en moyenne à la fin du tir. Une étude à plus grande échelle reste encore à réaliser afin de démontrer une efficacité de ce traitement prometteur. / Introduction Keloid scars (KS) are pathologies of skin healing causing often functional and aesthetic disturbances. They are linked to excess production and disorganization of collagen mostly due to TGF bêta; overproduction. The thermal lasers can improve healing through a modification of the inflammatory response. Indeed, a rise of temperature between 45 and 53 ° C leads to an overexpression of HSP 70, which causes a change in the expression of TGF bêta;. The 810nm laser diode has already proven to be effective but its wavelength cannot used on dark phototypes who are prone to developing KS.The objective of this study was to evaluate the effect of a thermal laser on keloids in animal and in the context of a clinical study.Determination of laser parameters Studies on skin explants, and on healthy volunteers have shown that 1210 nm was the most suitable wavelength for this indication because it is poorly absorbed by melanin. The laser parameters were also carefully determined in order to control the skin temperature elevation. For a 1210 nm laser diode, an irradiance of 5.1W/cm² for 10 seconds leads to a maximum temperature of 53 ° C.Development of a KS animal model. Since, there was no KS animal model of DC , an innovative one was developed for this specific study. Fragments of human KS including the dermis and epidermis were transplanted in 40 nude mice. A clinical and histological evaluation confirmed the successful integration of the graft. At 4 months, it was proven that the KS remained unchanged. Study of the 1210nm diode laser in an KS animal modelThe 1210 nm laser was evaluated on our KS animal model. Laser irradiation was performed on the grafts. Clinical and histological evaluations have shown no adverse reactions. A 45 ° C mean temperature was recorded during laser irradiation .Study of l the 1210nm diode laser after intrakeloid excision. Parallel to the animal study, a pilot study was performed to assess the feasibility and safety of a 1210nm diode laser irradiation. An intrakeloid excision was achieved; the suture was then irradiated for about 10 seconds. 20 patients were included in the study. The study is still ongoing. A 2-year follow up is scheduled. So far, it was noted that no harmful effects of the laser. 8 patients received injections of corticosteroids due to of keloid recurrence at six months.conclusionAn original KS animal model was developed for the first time to study of the in vivo effects of laser irradiation. It was demonstrated that a 1210nm diode laser (5.1W/cm², for 10 seconds) led to a 45°C skin temperature without any deleterious effect. The 1210 nm diode laser after intrakeloid excision showed no signs of toxicity in humans. In humans, the maximum temperature was 48 ° C +/- 3°C . A long term follow-up on a large series of patients is still necessary to confirm the effectiveness of this promising treatment.

With increasing demands for transit capacity of data networks as well as communication network optical networks seem to be the suitable solution. Light beam is attractive to use for data transmission . Transmitted data can be expressed by means of light impuls.. For execution of the project we need the whole optical telecommunical system which consists of transmitter, transmission link and receiver. The target of transmission link is to transfer optical beam from its resourse to detector with minimal losses. The optical fibre or optical freespace optical link FSO are used for this purpose. This thesis discusses basic effects that accompany these roads. The program that is created in this study clearly shows and describes the dependence of these phenomena on the individual input parameters. It is designed for students so that they can better imagine how these phenomena take place.

Organic semiconductors provide an alternative set of basis materials to fabricate electronic devices like PN Junctions, LEDs, and FETs. These materials have several benefits over traditional inorganic semiconductors including their mechanical flexibility, reliance on renewable resources, and inexpensive large-scale manufacturability. Despite the contemporary device implementations with organic semiconductors, a solid-state electrically-pumped organic laser diode does not exist. However, organically-based lasers do exist by utilizing the organic material strictly for optical gain. The challenge occurs when charge carriers appear in the organic material. The charge carriers must reach a concentration such that population inversion occurs producing optical gain. However, between the overlapping emission and absorption spectra of the organic material and insufficient carrier concentrations, positive optical gain remains elusive in electrically-pumped organic diodes. Organic device simulation provides a faster method of testing organic materials and device structures for positive optical gain based on known organic physics. The results generated from simulation provide key information in development of physical organic devices. This project produces a simulator capable of modeling current density and optical density with the intent of testing various device structures that allow for lazing in organic materials.

This master’s thesis deals with parameters and properties of electromagnetic wave, its spread in environment and then in optical fiber, as well with optical fibers. Principle of laser sources and a issues of coupling a optical performance into optical fiber are described here. Next a function of laser diodes, power and cooling requirements are described. A block diagram of fiber optic source of laser radiation is designed as well as a circuit solution of every single block with respecting of parameters and sensitivity of used laser diode. The protection of laser diode and high-frequency modulation of optical power are solved. Subsequently the construction of every single block was done and the right function of constructional solution was tested.