No description available.

In this thesis, a red green and blue (RGB) laser diode driver (LDD) is designed, assembled and tested, which can work as a standalone device or an internal component fully controlled by a laser projector. In particular, the thesis explores a multi-channel RGB LDD for a retrofitted laser projector, targeting projectors for home, business and education. If laser diodes (LDs) with the same color are connected in series, a higher forward voltage is required, making most commercial LDDs unsuitable for this application due to their insufficient compliance voltages. If the connections of all the LDs are in parallel, issues on size and cost arise since many LDs are used in this case. Another problem to use the commercial LDDs for RGB laser projection is that there are no proper communication interfaces to link the LDDs to the laser projector. In order to solve these problems by taking advantage of all the features of iC-HTG, an integrated circuit with automatic current control functionality, both the hardware circuits and the software for an eight-channel LDD are designed. Experimental results show that all the RGB channels can achieve compliance voltage of 23 V within the required working current range, which can drive up to 5 blue, 4 green or 10 red LDs in series in each single channel. It is confirmed experimentally that the designed LDD can fulfill the requirements on driving current (i.e. 1% accuracy and 1% stability). The protection functions of the developed LDD are also explored and verified experimentally. It can detect the open laser connection before the LDD channels are enabled. Fast over-current protection can be achieved within 1.5 µs. Circuit interfaces and protocols of the communications enable the multi-channel RGB LDD to work as a standalone device or an internal component of the laser projector. / Thesis / Master of Applied Science (MASc)

The effect of strain (stress) on the below threshold output of InGaAsP diode lasers has been investigated theoretically and experimentally. The degree of polarization (DOP) and the polarization- resolved spectral output (PRSO) were obtained as a function of the external stress applied to the device. A correlation between the DOP and the peak of the PRSO as a function of the stress was found. This correlation suggests that below threshold, DOP can be used to measure the strain in the active region of lasers. A model based on a strain modified Shockley matrix for the band calculation and a strain modified dipole moment for the optical emission has been constructed to bridge the correlation between the DOP and PRSO. / Thesis / Master of Engineering (ME)

Le remplacement des lasers à colorant émettant dans la gamme 550-570 nm, à l'aide de lasers solides, représente un véritable enjeu industriel. Les applications sont multiples tant dans le domaine de la recherche biomédicale que dans celui de la métrologie. Quelques solutions ont été développées à 561 nm et à 553 nm. Néanmoins, elles ne permettent pas de fournir des lasers intégrables parfaitement mono-fréquences émettant en continu un faisceau gaussien, d'une puissance supérieure ou égale à 200 mW. Dans ces travaux, nous proposons une étude théorique et expérimentale de cavités lasers solides monolithiques à base de Nd:YAG pompé par diode, doublé en fréquence en intra-cavité, à l'aide d'un cristal non-linéaire de KTP. Ces cavités, constituées de plusieurs cristaux, sont contactées par adhérence moléculaire. Elles ne contiennent aucune optique de mise en forme des faisceaux et présentent la particularité de comporter un double filtre de Lyot. Nous présentons les résultats obtenus avec des cavités émettant à 561 nm pour des puissances supérieures ou égales à 300 mW. Puis, après une étude statistique et une analyse des résultats de test de ces cavités à long terme (> 6000 heures), nous discutons des problèmes éventuels de fiabilité et nous suggérons des axes d'amélioration. Ayant réussi à faire osciller, pour la première fois, la raie à 1106 nm du Nd:YAG, nous montrons ensuite la faisabilité d'un laser compact mono-fréquence continu à 553 nm, émettant une puissance de 200 mW à 500 mW avec un rendement de conversion pompe/laser visible de l'ordre de 19 %. Pour conclure, nous montrons qu'il est possible, dans des cavités de ce type, de faire osciller des raies Raman issues des raies fondamentales et de les doubler en fréquence en intra-cavité. Nous ouvrons ainsi la porte à toute une famille de lasers solides émettant dans la gamme 540-600 nm. / Replacement of dye lasers emitting in the range 550-570 nm, using solid state lasers, is a real industrial issue. There are many applications both in the field of biomedical research than in metrology. Some solutions have been developed for 561 nm and 553 nm. However, they do not provide fully integrated lasers emitting single-frequency continuous Gaussian beam with a power equal or up to 200 mW. In this work, we propose a theoretical and experimental study of solid monolithic cavity lasers based on Nd:YAG diode-pumped, frequency-doubled intra-cavity, using a non-linear crystal of KTP. These cavities, consisting of several crystals, are contacted by molecular adhesion. They contain no optical layout of the beams and they have the particularity of including a double Lyot filter. We present the results obtained with those cavities emitting at 561 nm for powers greater than 300 mW. Then, after a statistical study and analysis of test results of these cavities in the long term (> 6000 hours), we discuss about the potential problems of reliability and we suggest areas for improvement. For the first time, we show that the line at 1106 nm of the Nd: YAG can oscillate in this type of cavity. Then we demonstrate the feasibility of a compact single-frequency laser at 553 nm continuously, emitting a power of 200 mW to 500 mW with a conversion efficiency of pump / visible laser of about 19%. Finally, we show that it is possible, in cavities of this type, to oscillate the Raman lines from the lines of the fundamental and doubled frequency in intra-cavity. We open the door to a whole family of solid state lasers emitting in the range of 540-600 nm.

No description available.

A series of rapid, high sensitivity capillary electrophoresis (CE) separation systems have been developed for the analysis of biological analytes and systems. A majority of the work has focused on development of novel instrumentation, in which new injection and detection strategies were investigated to improve the sensitivity of fast CE. A novel optical injection interface for capillary zone electrophoresis based upon the photophysical activation of caged dye attached to the target analyte was developed. The primary advantage of this approach is the lower background and background-associated noise resulting from reduced caged-fluorescein emission in conjunction with the high quantum yield of the resulting fluorescein. Improved detection limits were obtained compared to those observed in photobleaching-based optical gating. A primary drawback of photolytic optical gating CE is the lack of available caged-dye analogs with sufficiently fast reaction kinetics for online derivatization. To overcome this limitation, we have developed a chemical derivatization scheme for primary amines that couples the fast kinetic properties of o-phthaldialdehyde (OPA) with the photophysical properties of visible, high quantum yield, fluorescent dyes. The feasibility of this approach was evaluated by using an OPA/fluorescent thiol reaction, which was used to monitor neurotransmitter mixtures and proteins. The utilization of a high power ultraviolet light emitting diode for fluorescence detection in CE separations has been introduced to analyze a range of environmentally and biologically important compounds, including polyaromatic hydrocarbons and biogenic amines, such as neurotransmitters, amino acids and proteins, that have been derivatized with UV-excited fluorogenic labels. To understand cellular chemistry, it is imperative that single cells should be studied. This work was focused on developing CE based method to characterize the cellular uptake of TAT-EGFP. We demonstrated TAT mediated delivery of EGFP protein into HeLa cells and TAT-EGFP loaded single cell was analyzed by CE-LIF to determine the intracellular EGFP content. An application of CE-LIF for the determination of biogenic amine levels in the antennal lobes of the Manduca sexta is also explored and methods were developed to analyze a single antennal lobe dissected from moths. The lobe was digested and contents were labeled with the fluorogenic dye prior to CZE analysis.

Self-heating can have a detrimental effect on the performance and reliability of high power microwave devices. In this work, the thermal performance of the gallium arsenide (GaAs) Gunn diode was studied. Infrared (IR) thermal microscopy was used to measure the peak operating temperature of the graded-gap structured device. Temperature measurements were experimentally validated using micro-thermocouple probing and compared to values obtained from a standard 1D thermal resistance model. Thermal analysis of the conventionally structured Gunn diode was also undertaken using high resolution micro-Raman temperature profiling, IR thermal microscopy and electro/thermal finite element modeling. The accuracy of conventional IR temperature measurements, made on semiconductor devices, was investigated in detail. Significant temperature errors were shown to occur in IR temperature measurements made on IR transparent semiconductors layers and low emissivity/highly reflective metals. A new technique, employing spherical carbon microparticles, was developed to improve the measurement accuracy on such surfaces. The new ‘IR microparticle’ technique can be used with existing IR microscopes and potentially removes the need to coat a device with a high emissivity layer, which causes damage and heat spreading.

This paper reviews the analytical strategy employed in conventional p-n junction. Then it goes through the analysis of magnetic p-n junction in the same strategy, which makes the review of magnetic p-n junction succinct. I-V equation of magnetic diode is the result of the p-n junction analysis. However, of great importance is to form an acceptable ohmic contact on magnetic diode, which is assumed to be ideal during the magnetic p-n junction analysis. The paper moves on to ohmic contact for magnetic diode, with the example of GaN based magnetic material. With the calculation of the shift of Fermi level in n-GaN with band splitting, conventional ohmic contact structure for n-GaN can be employed to magnetic n-GaN. Experiments from one group prove it. Ohmic contact optimization experiment on n-GaN is present. Ni/Au deposition on n-GaN shows an acceptable ohmic contact. The outlook part points out that the way for research on Schottky diode on magnetic material is partially paved by contents included in this paper.

Este trabalho apresenta a fabricação e a caracterização elétrica de contatos Al/Ti/Ni(Pt)Si sobre junções rasas N+P com aproximadamente 0,2 ìm de profundidade, sendo que o monosiliceto de níquel foi formado a partir da estrutura Ni(30nm)/Pt(1,5nm)/Si. O comportamento elétrico dos diodos obtidos no melhor processo foi adequado, com as seguintes médias e desvios padrões: corrente reversa por unidade de área de 33,8nA/cm2 ±12,3 nA/cm2 e corrente reversa por unidade de perímetro de 654pA/cm ±229pA/cm para tensão reversa de -5V, a resistência reversa dos diodos quadrados de 268,9G? ±97,7G? e a resistência reversa dos diodos serpentinas de 35,5G? ±11,5G?, a tensão de início de condução resultou entre 0,55V e 0,56V, a resistência série em condução de 4,7? ±1,3?, fator de idealidade de 1,15 ±0,03, e corrente de saturação de 1,1x10-11A para diodos quadrados (300ìm x 300ìm). O menor valor de resistividade do filme de (Ni(Pt)Si) resultou 25ì?cm e a resistência de folha de 3,13 ?/? foram obtidas após a formação do mono-siliceto de níquel na temperatura de 600 ºC durante 120 segundos. As estruturas Kelvin apresentaram resistividade de contato de 15,0ì?.cm2 ±3,3ì?.cm2 e comportamento ôhmico estável para diversos níveis de corrente. Após uma extensa análise sobre modelagem de contato, foi elaborado um programa computacional desenvolvido em MATLAB, baseado em um método bem conhecido, isto é, uma malha de resistores tridimensional, que analisa os efeitos do fenômeno de concentração das linhas de corrente lateral no contato. Este programa foi aplicado em contatos com siliceto de níquel, onde foram observadas reduções de até 32% na resistividade real do contato. / This work presents the fabrication and electrical characterization of Al/Ti/Ni(Pt)Si contacts having the nickel monosilicide formed from Ni(30nm)/Pt(1.5nm)/Si structure on shallow N+P junctions with about 0.2 ìm of depth. The diodes? electrical behavior achieved at the best process was considered good, with the following average and standard deviations: area diode leakage current of 33.8nA/cm2 ±12.3nA/cm2 and periphery diode leakage current of 654pA/cm ±229pA/cm for reverse voltage of -5V, the square diode reverse resistance of 268.9G? ±97.7G? and serpentine diode reverse resistance of 35.5G? ±11.5G?, forwardbias voltage between 0.55V and 0.56V, forward series resistance of 4.7? ±1.3?, ideality factor of 1.15 ±0.03, and reverse saturation current of 1.1x10-11A for square diodes (300ìm x 300ìm). The lowest film resistivity value (Ni(Pt)Si) of 25ì?cm and sheet resistance of 3.13 ?/? were obtained for the formation of nickel monosilicide under temperature of 600ºC for 120 seconds. The cross-bridge Kelvin resistors presented contact resistivity of 15.0 ì?.cm2 ±3.3 ì?.cm2 and stable ohmic behavior for several electrical current levels. After extensive analysis about contact modeling, a computer program was elaborated in MATLAB, based on a well-known three-dimensional resistor network, which analyses the lateral current crowding effects on contact. This program was applied for contacts with nickel silicide, where a decrease up to 32% at the real contact resistivity was observed.

A terapia laser é um excelente procedimento clínico coadjuvante no tratamento endodôntico pela sua capacidade de promoção e melhoria da limpeza e da desinfecção do sistema endodôntico, porém existem poucos estudos sobre a possível utilização desta nova tecnologia nas situações clínicas de desobturação. O objetivo deste estudo foi avaliar in vitro o uso do laser de diodo (810nm, no modo contínuo) na desobturação da guta percha e do cimento AH Plus, utilizando ou não solvente químico (eucaliptol). Canais radiculares obturados tiveram o seu material obturador irradiado pelo laser de diodo de 810 nm (ZAP SOFTLASE, ZAP LASERS). A temperatura externa radicular durante a irradiação foi verificada no terço apical de 12 amostras utilizando o sistema de medida de temperatura. Observou-se um aumento de temperatura que variou de 2,47 a 9,35 ºC. Raízes foram divididas aleatoriamente em 4 grupos com 10 espécimes, variando o parâmetro de irradiação laser e a utilização do eucaliptol. Os grupos foram: Grupo I = irradiação (1,0 W) sem a utilização de solvente, Grupo II = irradiação (1,5 W) sem o uso de solvente, Grupo III = irradiação (1,0 W) + solvente, Grupo IV = (1,5 W) + solvente. As amostras foram radiografadas no sentido V-L e M-D, antes e após o retratamento, digitalizadas, e as áreas remanescentes de guta percha foram calculadas com o auxílio de programas de computador: Adobe Photoshop e ImageLab. Os resultados dos espécimes dos grupos: G1xG3; G1xG4; G2xG4 apresentaram diferença estatística. O modelo experimental selecionado permitiu verificar que a propagação da temperatura durante o procedimento não excedeu 10ºC e que a presença do solvente possibilitou a remoção de maior quantidade de material obturador auxiliando o processo de desobturação quando do emprego da irradiação com laser de diodo. / The laser therapy is an excellent adjunct clinical procedure in endodontic treatment in order to improve the cleaning and disinfection of the root canal system; however few studies in the literature investigated the possible use of this new technology in the clinical situations of retreatment. The objective of this study was to evaluate in vitro the use of the diode laser (810nm, continuous mode) in the removal of gutta-percha and AH Plus sealer from the root canal, with or without the use of a chemical solvent (eucalyptol). Root canal filling materials were irradiated by 810 nm diode laser (ZAP SOFTLASE, ZAP LASERS). The temperature changes at the outer root surface were verified in the apical third of 12 samples during the irradiation. Temperature increase from 2.47 to 9.35 ºC was observed. The specimens were randomly divided in 4 groups of 10 roots each, varying the parameter of laser irradiation and the use of eucalyptol. The groups were assigned as follow: Group I = irradiation (1.0 W) without the solvent use, Group II = irradiation (1.5 W) without the solvent use, Group III = irradiation (1.0 W) + solvent, Group IV = (1.5 W) + solvent. Mesio-distal and buccolingual radiographs were taken before and after retreatment and the area of remaining gutta-percha in the root canals was determined with the aid of: Adobe Photoshop and ImageLab softwares. The groups: G1xG3; G1xG4; G2xG4 presented statistical differences.Based on the methodology used, it was verified that the temperature did not exceed 10ºC and that the presence of the solvent made it possible to remove large amounts of root canal filing material, aiding the desobturation process when used in association to the diode laser.