This paper is to present the measurement of high-speed traveling-wave electroabsorption modulator (TW-EAM). A traveling-wave electrode structure can overcome RC limitation and allows longer device for the high-speed performance. Low driving voltage, high extinction ratio and high optical saturation power can thus be obtained. Two structures of TW-EAMs are taken as examples, namely ridge- (ri-) and undercut-etching-active (un-) types. The topic of this work includes all the electrical, optical and electrical-to-optical measurement for the characterization of TW-EAM. The characterization on EAM is divided by three steps : electrical-to-electrical, optical-to-optical and electrical-to-optical measurement. Firstly, by using a 40GHz vector network analyzer, the microwave-propagation loss and reflection loss are extracted from scattering-parameters (S-parameters). Secondly, the optical propagation loss in waveguide is obtained by comparing the optical transmission of different lengths of EAMs. Finally, the electrical-to-optical response is obtained by transferring the high-speed-modulated optical signal to electrical signal by a high-speed photodetector. It has been shown that the un-TW-EAM can have advantages over the ri- types due to the lower microwave and optical propagation loss.

Chirp parameter plays an important role in the optical communication system. In this paper, we use a simple method to extact the chirp parameter, where the electroabsorption modulators (EAM) and broad-band Cr:YAG crystal-fiber are two main devices to be measured. A high-speed vector network analyzer (VNA) and a 50km non-zero-dispersion single-mode fiber (SMF) are used in this method. Modulating and detecting the optical power by the VNA signal, the chirp-parameters can be obtained by launching the chirped-optical signal into the SMF. It shows that this method is a reliable tool for analysis of chirp on fiber-based devices. Generally, EAMs have high-speed performance, however the chirp behavior still is a dominated factor on long optical fiber transmission. When changing the wavelength of input optical power and DC-bias applying on EAMs, the chirp parameters will be varied. Our measured results showed that the chirp parameters of the EAMs are in a low range of from ¡V1 to 1. These low values give an indication that it is quite useful for long-distance optical fiber transmission. We also measured the chirp parameter of Cr4+: YAG crystal fiber. Its ASE spectrum covers the whole communication wavelength (1300nm to 1600nm) and the absorption wavelength is in near-infrareds ranges (980nm to 1100nm). Therefore, this kind of materials can be potentially used for most of the telecommunication fields used today, like fiber-based optical amplifier, ASE, laser ¡K and so on. In order to further investigate the performance of Cr4+: YAG crystal fiber, the ASE, optical gain and the chirp behaviors are also measured in this paper.

Semiconductor Electroabosortion Modualtor (EAM) has become an important element in optical fiber communications because of its capability to integrate with other semiconductor devices, high-speed and low driving voltage. However, high optical insertion loss and low tolerance in optical power coupling are main general problems to be solved in order to get high electro-optical (EO) efficiency. Monolithically integrating EAM with optical spot-size converter (SSC) can lead to high-efficiency single-mode fiber coupling, but the price is on the complex fabrication methods. In this paper, based on previous work, the selective undercut etching active region (UEAR) and the whole wet-etching techniques are employed to fabricate the integration of laterally tapered SSC and EAM. Also, by applying the ion-implantation in SSC region, the reliable transfer efficiency and also high-speed performance are obtained based on the high resistance and low parasitic capacitance in SSC. The active region containing 10 strain compensated multiple-quantum-wells (MQWs) sandwiched by n-InP (bottom) and p-InP (top) for the electroabsorption region of EAM and also the top region of lateral tapered SSC. The converted waveguide in SSC consists of alternating InGaAsP and InP layers. An HBr-base etching solution is first used to define the top p-cladding with the widths of from 6um to 8um. An H2O2-base solution is then utilized to selectively undercut-etch the MQWs from InP material. The active waveguide p-cladding in EAM is set as 8um. After defining EAM and SSC, the converted waveguide is fabricated by aligning the top SSC and then wet-etched. By using an e-beam evaporator, Ti/Pt/Au and Ni/AuGe/Ni/Au are deposited as p- and n-type metallization, respectively. PMGI is spun serving as the passivation, planarization and bridging. The microwave coplanar waveguide (CPW) line is finally defined by depositing Ti/Au for microwave load- and feed- lines and connecting EAM. The length of SSC is 350um. The Spot-Size Converter monolithically integrated with Electroabsortion Modulator using whole wet-etching technique is demonstrated. ¡V12.5dB of fiber-to-fiber insertion loss and 10dB (TE) 10dB(TM) extinction ration in 1V(1570nm excitation) is obtained in this device. Using Fabry-Perot method, the average optical transfer loss in SSC is extracted to be 2dB, quite consistent with simulation results. By applying ion-implantation on SSC, the broadband EO performance 45GHz of ¡V3dB bandwidth is achieved for 100um long device due to the low capacitance and the high resistivity in SSC.

The band-gap engineering is an important technique for integration of optoelectronic devices. Using the inter-diffusion of atoms in the quantum well structure, Quantum-Well Intermixing (QWI) technique has been widely used for band-gap engineering due to its simple process and capability of local tuning in chip. Electroabsorption modulator (EAM) and semiconductor optical amplifier (SOA) are two essential devices in optoelectronic field. The band-gap engineering is needed to get optimized performance in integration of EAM and SOA because of the energy level offset in both material structures. In this work, an simple QWI technique, called impurity free vacancy diffusion (IFVD), is employed to integrate EAM and SOA. In the device design, a chain structure of EAM-integrated SOA is used for high-speed and low-noise performance. No re-growth step is needed in the whole device process. An good property EAM with blue shift of 20nm from SOA portion is achieved from this IFVD method.

The electroabsorption modulators (EAM) play an important role in the optoelectronic integrated circuits. InGaAs/InAlAs is an excellent material system for fabricating 1.55-£gm EA modulators. Natural high band-offset ( ) ratio structure and the strong exciton effect make this kind of material a good candidate for high saturation power operation and high speed. In order to design good quantum-well (QW) for electroabsorption, the Vegard¡¦s law is used to obtain the parameters of In1-x-yGaxAlyAs material by interpolating the relevant binary semiconductor material. The bowling factor is included in finding the right bandgap. Using the Resonant Scattering Method, the QW energy levels and electron-hole overlap integrals can be obtained to calculate the optical electroabsorption effects. In this thesis, the TWEAM based on In1-x-yGaxAlyAs material is also fabricated. In order to get low parasitic capacitance for high-speed operation, a processing called undercut-etching the active region is developed in this work. A selective etching solution (citric acid : H2O2) is used to etch InGaAs layers from InAlAs and the undercut-etching structure InGaAlAs EAM has been successfully fabricated. The processing includes 1)optical waveguide formation with wet etching; 2)n-contact evaporation and contact annealing; 3)mesa etch, PMGI passivation/bridging/planarization; 4)final metallization, cleaving line formation, wafer lapping and device cleaving.

Ultra Wide Band (UWB) is a short-pulse electrical signal which is widely used for short distant wireless communication because its low path loss, good immunity to multipath propagation, and high data rate. The reason of using optical fiber as carrier is fiber can bust up the communication capacitance in long distance range because of high capacitance, low loss propagation. Thereby, the technique of UWB signal on fiber has become more and more important. In this work, a novel method using electro-absorption modulation with short termination for interface of optical fiber and generate UWB signal is proposed and demonstrated. The structure is simple.This method don¡¦t need employing any complicated frequency mixer, or complex systems. This work need to generate optical pulse with high energy, which is feded into the EAM. The signal can generate electrical pulse and build electrical field on EAM in the same time. The optical pulse is modulated by the electrical field on EAM. Using this way, we can generate UWB optical signal.

Molecular dynamics (MD) simulations were used in order to investigate structure and mechanical properties of zirconium and zirconium hydride. Calculation of temperature dependent failure of zirconium, diffusion of hydrogen in zirconium, properties of interfaces in zirconium and zirconium hydride and effect of hydrogen on crack nucleation and propagation were in good agreement with available experimental data. These are the first computer simulations where large-scale atomic/molecular massively parallel simulator (LAMMPS) code was used with the Embedded Atom Method (EAM) and Modified Embedded Atom Method (MEAM) to study structure and mechanical properties of zirconium hydrogen system (Zr-H) and zirconium hydride (ZrH2). Verification of methods was done in order to establish the best potential for zirconium and zirconium hydride. EAM and MEAM potentials successfully predicted lattice parameters, mechanical properties and variation of lattice parameters with temperature for α-Zr. MEAM potential was used to predict correctly the face centered structure for ZrH2 and also its mechanical properties. Temperature dependent stress-strain curves were calculated in order to predict yielding point for α-Zr. Results indicate early yielding and failure with increase of temperature in zirconium on application of tensile and compressive strains. Anisotropic stress variation with temperature in α-Zr was calculated. Hydrogen ingress through diffusion of hydrogen in zirconium is a mechanism responsible for formation of hydrides. Temperature-dependent hydrogen diffusion and activation energy for diffusion was calculated and the agreement with experiments was satisfactory. Anisotropy of diffusion of hydrogen is observed for Zr crystal. Hydrogen diffusion was also modeled under tensile and compressive strain and a possible formation of hydrides in the direction perpendicular to applied strain was observed. The effect of strain on orientation of hydride was investigated. Hydride {111} oriented crystal was strained along [1 1 ̅ 0] and [111] direction. Energy as a function of strain is calculated along both directions [111] and [1 1 ̅ 0] and it was found that energy of the system increase with increase in strain along [1 1 ̅ 0] and decrease with increase of strain along [111] direction. Calculated stress and strain curves indicate lower stresses along [111] direction and this causing the hydride to reorient in a direction perpendicular to applied strain. Structure of the interface (0 0 0 1) α-Zr // {1 1 1} δ-ZrH2 is modeled in order to investigate the crack initiation at this interface. Interfacial cracking of hydride under stress is observed. This observation is in good agreement with available experimental studies. Cracks are seen to nucleate earlier at higher temperature. Cracks and voids are common defects in zirconium fuel cladding. A crack is modeled along (0 0 0 1) plane of zirconium with hydrogen. In the presence of hydrogen cracks nucleate in zirconium causing fracture. This observation is in good agreement with previous experimental studies. Bonds surrounding atoms and stress concentration analysis were performed using OVITO and VMD software’s respectively. Weaker bonds and higher stress concentrations are observed in the presence of hydrogen in zirconium. The presented results clearly demonstrate that MD simulation can be used to predict structure and processes that are important for understanding failure in Zr based nuclear materials.

El presente proyecto se realizó para la empresa Bionet S.A., esta organización se dedica a la importación y comercialización de materiales de laboratorio y tecnología educativa, sus actividades principales se orientan hacia la participación de procesos de licitación así como también, la venta de equipos y material educativo a instituciones, colegios y universidades. En ambas situaciones el área de ventas recibe el pedido y realiza manualmente un documento adjuntando información necesaria para la toma de decisiones del cliente, a este documento lo llamaremos cotización. La empresa recibe 83 solicitudes a la semana entre entidades públicas y privadas de las cuales solo cotiza 56, para esta actividad se utilizan más de 50 catálogos de productos de diferentes marcas y en diferentes idiomas. El propósito de la presente investigación consistió en la implementación de un sistema que permita automatizar el proceso de realización de cotizaciones, minimizando el tiempo en que estas tomaban en ser realizadas de forma manual, para ello se realizó una distribución de de contenidos con esto nos referimos a la forma de organizar los elementos que componen el catalogo general de la empresa, como documentación técnica, contenido gráfico u otros que contenga información relevante para los usuarios, siendo almacenados en una única base de datos. También se logró predecir beneficios futuros, aumentar la capacidad de producción y por ende las oportunidades de venta. Fue necesario el estudio de metodología para el desarrollo de aplicaciones Web, métodos de seguridad para el servidor Web y control de acceso, entre otros. El presente proyecto se justificó por cuanto posee valor teórico y utilidad práctica en base a los beneficios que ha generado.

I have used the Embedded Atom Method (EAM) to investigate the vibrational behaviors of a large number of metallic systems. The systems examined are the bulk bcc metals Li, Na, K, Rb, Cs, Nb, Ta, Mo, W, and Fe, the bulk fcc metals Ni, Cu, and Al, the (100), (110), (111), and (211) surfaces of the Li, Na, K, Rb, and Cs, and the (100), (110), and (111) surfaces of Ni and Cu. I have conducted a more detailed and extensive review of existing EAM models and their ability to characterize bulk vibrational behavior than has ever previously been reported. I show the ability of an EAM model to quantitatively predict the vibrational properties of the bulk alkali metals in excellent agreement with experiment. The present work remedies a lack of computational investigation into bcc metallic surfaces by performing lattice dynamics calculations of the (110), (100), (111), and (211) alkali metal surfaces. Additionally, I present lattice dynamics calculations on the (111), (100), and (110) surfaces of Cu and Ni. An accurate set of surface Debye temperatures for these metal surfaces has been calculated. The extensive number of metals and planar geometries studied has enabled the identification and clarification of general relationships between surface phonons, surface coordination, and atomic density. The changes in vibrational behavior due to the truncation of the bulk near a surface can be understood by the consideration of three things: the vibrational behavior of a 1-D chain of harmonic oscillators, the bulk dispersion relation in the direction perpendicular to a surface, and the atomic coordination of near surface atoms. In general, relaxation causes force constants between atoms to stiffen, resulting in higher vibrational frequencies. The impact of stiffening on the vibrational characteristics depends largely on the surface geometry, as well as the particular properties of the metal. It can cause new surface modes and resonances, or cause surface vibrations to be more strongly coupled to the vibrations of bulk atoms.

Engineering asset management (EAM) is a new concept about inter-disciplinary field that combines technique issues of asset reliability, safety and performance with financial and managerial requirements. However, there are few literatures in research and application cases from industries. This thesis takes the Five hundred meters Aperture Spherical Telescope (FAST) project as a case to explore how EAM was processed in large engineering projects. The aim of this study is to figure out the key elements of EAM in the projects like FAST and to develop an EAM model that is suitable for this kind of projects. FAST will be the biggest single radio telescope in the world, that being built in a natural Karst basin in Guizhou, China. In this study, qualitative research and case study were adopted. The related knowledge of EAM was collected from the scientific literature, which helped access the initial theoretical framework. The details of FAST project, which includes the fundamental data and the first-hand information, are from the interviews and surveys. By applying EAM to the project management of FAST, the shortcoming of existing EAM model has been noticed. The existing model mainly focuses on cost-saving and profit-achieving, while ignoring environment and risk management. In order to make EAM model more efficient and practical, this thesis provides a tailored EAM model that could be suitable for large engineering projects like FAST.