Development of hybrid UV VCSEL with organic active material and dielectric DBR mirrors for medical, sensoric and data storage applications

Lasers play an important role for medical, sensoric and data storage devices. This thesis is focused on design, technology development, fabrication and characterization of hybrid ultraviolet Vertical-Cavity Surface-Emitting Lasers (UV VCSEL) with organic laser-active material and inorganic distributed Bragg reflectors (DBR). Multilayer structures with different layer thicknesses, refractive indices and absorption coefficients of the inorganic materials were studied using theoretical model calculations. During the simulations the structure parameters such as materials and thicknesses have been varied. This procedure was repeated several times during the design optimization process including also the feedback from technology and characterization. Two types of VCSEL devices were investigated. The first is an index coupled structure consisting of bottom and top DBR dielectric mirrors. In the space in between them is the cavity, which includes active region and defines the spectral gain profile. In this configuration the maximum electrical field is concentrated in the cavity and can destroy the chemical structure of the active material. The second type of laser is a so called complex coupled VCSEL. In this structure the active material is placed not only in the cavity but also in parts of the DBR structure. The simulations show that such a distribution of the active material reduces the required pumping power for reaching lasing threshold. High efficiency is achieved by substituting the dielectric material with high refractive index for the periods closer to the cavity. The inorganic materials for the DBR mirrors have been deposited by Plasma- Enhanced Chemical Vapor Deposition (PECVD) and Dual Ion Beam Sputtering (DIBS) machines. Extended optimizations of the technological processes have been performed. All the processes are carried out in a clean room Class 1 and Class 10000. The optical properties and the thicknesses of the layers are measured in-situ by spectroscopic ellipsometry and spectroscopic reflectometry. The surface roughness is analyzed by atomic force microscopy (AFM) and images of the devices are taken with scanning electron microscope (SEM). The silicon dioxide (SiO2) and silicon nitride (Si3N4) layers deposited by the PECVD machine show defects of the material structure and have higher absorption in the ultra violet range compared to ion beam deposition (IBD). This results in low reflectivity of the DBR mirrors and also reduces the optical properties of the VCSEL devices. However PECVD has the advantage that the stress in the layers can be tuned and compensated, in contrast to IBD at the moment. A sputtering machine Ionsys 1000 produced by Roth&Rau company, is used for the deposition of silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum oxide (Al2O3) and zirconium dioxide (ZrO2). The chamber is equipped with main (sputter) and assisted ion sources. The dielectric materials were optimized by introducing additional oxygen and nitrogen into the chamber. DBR mirrors with different material combinations were deposited. The measured optical properties of the fabricated multilayer structures show an excellent agreement with the results of theoretical model calculations. The layers deposited by puttering show high compressive stress. As an active region a novel organic material with spiro-linked molecules is used. Two different materials have been evaporated by utilizing a dye evaporation machine in the clean room of the department Makromolekulare Chemie und Molekulare Materialien (mmCmm). The Spiro-Octopus-1 organic material has a maximum emission at the wavelength λemission = 395 nm and the Spiro-Pphenal has a maximum emission at the wavelength λemission = 418 nm. Both of them have high refractive index and can be combined with low refractive index materials like silicon dioxide (SiO2). The sputtering method shows excellent optical quality of the deposited materials and high reflection of the multilayer structures. The bottom DBR mirrors for all VCSEL devices were deposited by the DIBS machine, whereas the top DBR mirror deposited either by PECVD or by combination of PECVD and DIBS. The fabricated VCSEL structures were optically pumped by nitrogen laser at wavelength λpumping = 337 nm. The emission was measured by spectrometer. A radiation of the VCSEL structure at wavelength 392 nm and 420 nm is observed.

CoDaPack. An Excel and Visual Basic based software of compositional data analysis. Current version and discussion form upcoming versions

In the eighties, John Aitchison (1986) developed a new methodological approach for the statistical analysis of compositional data. This new methodology was implemented in Basic routines grouped under the name CODA and later NEWCODA inMatlab (Aitchison, 1997). After that, several other authors have published extensions to this methodology: Marín-Fernández and others (2000), Barceló-Vidal and others (2001), Pawlowsky-Glahn and Egozcue (2001, 2002) and Egozcue and others (2003). (...)

Who or what was the inspiration for choosing your current course of study?

Award winning student essay. This essay won the Student Writing Award Scheme via the HE Academy Subject Network for Information and Computer Sciences.

La reintegración social y económica de los grupos armados ilegales en Colombia: reflexiones a partir de la trayectoria de nueve excombatientes

Esta investigación toma como marco general la Política de Reintegración Social y económica de personas y grupos alzados en armas en Colombia, en donde tras el estudio de las trayectorias en el conflicto de un grupo de 9 excombatientes, se aborda la relación existente entre los beneficios otorgados por dicha política y aquello que facilitó y motivó el ingreso, la permanencia y desmovilización de los grupos armados. Se presenta una caracterización e interpretación conceptual de las denominadas trayectorias en el conflicto, son establecidas relaciones y diferencias entre las organizaciones ilegales FARC y las AUC, se revisan las percepciones que frente a los beneficios del programa de reintegración tienen excombatientes y profesionales de la entidad que lidera dicho proceso y a partir de ello, es argumentada la incidencia que sobre el éxito de esta política tienen las características individuales y particulares, tanto de los excombatientes como de las organizaciones armadas ilegales.

Current status of knowledge about suicide in people with cancer

Aim: To review the current knowledge about suicide in cancer patients. Method: We searchedspecialized databases using keywords for articles published in the last two decades (1990-2010),and compiled and reviewed them in order to: indicate the prevalence of suicide in cancer patientsworldwide and in Colombia, differentiating the data by sex and age; establish the types of cancerthat are associated with suicide, identify risk factors for committing or considering suicide andpresent the strategies of professional and psychological intervention directed at cancer patientswith suicidal ideation and suicide attempts. The present article is a review of the information on thesubject. Results: We found that: in cancer patients, the suicide rate is two times higher thanin the general population; depression, suicidal ideation and location of cancer are some of therisk factors for suicide, and there is a lack of published guidelines for professional managementof the suicidal patient with cancer. Conclusion: The need to carry out research on the topic ofsuicide in cancer patients was established.

Description and analysis of pulmonary rehabilitation care programs current state in four cities of Colombia

Purpose: there are many studies reporting the benefits of pulmonary rehabilitation, but few of them exhibit the behavior and activities of these services. This article presents the characteristics of services, parts management and training level of team members, in addition to the variables or instruments used to measure the effectiveness and impact in these programs. Method: it was made a cross sectional convenience sample which included seven pulmonary rehabilitation services in four Colombian cities (Bogotá, Medellín, Manizales and Cali), selected by the coverage, for having at least one year of experience and for being formally established and recognized nationwide. The interdisciplinary team of each service answered a survey that was validated through a pilot test and expert consensus. Participation was voluntary. Results: labor onset pulmonary rehabilitation services correspond to an average of a decade, with COPD and asthma pathologies of attention. The programs are characterized by an outpatient treatment with an average duration of eight to twelve weeks, with a frequency of an hour three times a week. Also, the director of the service is regularly a pulmonologist and the coordinator a physiotherapist (57.14%). The posgradual training of these professionals is notable, and they report to have procedural, administrative and communicative skills, but qualify regular there research skills. The physical and technological resources are well tested. 71.42% have done impact studies, but only 28.57% have been published. All have in common training in upper limbs, lower limbs, respiratory muscles, counseling, functional assessment and quality of life. The effectiveness and impact of programs is measured by the walking test, quality of life questionnaires and activities of daily living.

Productividad de autores y revistas en el área de la excepcionalidad : un análisis bibliométrico a través del Current Index to Journals in Education.

Delimitar el área de las dificultades del aprendizaje y conocer la panorámica actualizada de la investigación en esta área. El Current Index Journal Education (CIJE): todos los abstracts aparecidos bajo el epígrafe handicapped and gifted children, en el período 1980-1984, ambos inclusive. Estudio de la productividad de revistas. Impacto, vida media y ranking de las más productivas. Estudio de productividad de autores. Análisis de los autores más productivos. CIJE. Investigación bibliométrica: ley de Lotka, ley de dispersión de Bradford, índice de productividad total, índice de productividad fraccionaria, agrupamiento criterial de Crane. En cuanto a las revistas se codifican 81, con un total de 7287 artículos, siendo la media global de 90 artículos por revista. Una sola revista publica el 70 por ciento de la producción total. Con la ley de Bradford se hallan cuatro áreas de productividad: la primera área la forman cinco revistas que publican una media de 371'6 artículos. La segunda la forman 15 títulos con una media de 184'4 artículos, la tercera la forman 21 títulos con una media de 90 artículos. La cuarta la forman 40 títulos con una media de 42'2 artículos. Las revistas de las dos primeras áreas se publican todas en EEUU, excepto una. Para la jerarquización de autores se recurre al modelo de Crane: se encuentran 29 autores a los que incluir en grandes productores, 150 en el de productores moderados, 1220 aparecen como aspirantes y 5'190 como transeuntes. Los autores más productivos son: Frith, G., Kavale, K. A., Chandler, H. N., Torrance, E. Paul, Salend, S. J., Algozzine, B., Csapo, M., Forness, S., Stainback, W., Stainback, S., Ysseldike, J. Giordano, G. y Treffinger, D. Sería interesante realizar un estudio de las áreas temáticas.

Methodology in language teaching : an anthology of current practice.

Ofrece una visión general de los enfoques actuales, problemas y prácticas en la enseñanza del inglés como segundo idioma. La antología contiene más de cuarenta artículos ,organizados en dieciséis secciones, publicados principalmente en la última década. Presenta un panorama general de la enseñanza del inglés e ilustra la complejidad de la planificación de muchas actividades fundamentales. Estas actividades incluyen la enseñanza del inglés en primaria, secundaria y enseñanza superior; formación del profesorado. Examina los conocimientos lingüísticos; planes de estudio y desarrollo de materiales, el uso de computadoras y otras tecnologías en la enseñanza, así como la investigación sobre diferentes aspectos del aprendizaje de un segundo idioma. También se incluyen dos series de preguntas de discusión: un conjunto de antecedentes prelectura y una reflexión posterior a la lectura.

Teacher education for content and language integrated learning : insights from a current European debate

Monogr??fico con el t??tulo: "Estrategias innovadoras en la formaci??n del profesorado"

Musem Training Institute - its current status

Museum Training Institute: Kershaw House, 55 Well Street, Bradford, BD1 5PS Britain’s system of vocational training and qualifications has been undergoing a fundamental revolution in recent years. The single most important feature of this revolution is the concept of competence - the ability to perform to the standards required in employment. It is in recognition of this ability that National and Scottish Vocational Qualifications are awarded.

Central auditory processing: a current literature review and summary of interviews with researchers on controversial issues related to auditory processing disorders

This paper discusses issues related to Auditory Processing Disorders (ADP) evaluation and management, focusing mainly on the disorder in children.

Current infection control trends in audiology

The purpose of this study was to provide an in-depth assessment of current infection control practice trends in a group of practicing audiologists. The study investigated the extent to which Universal Precautions are applied in the clinical settings, the percentages of respondents familiar with general infection control nomenclature, and the future educational directives.

Current Trends in Hearing Assistance Technology

A survey was distributed to practicing audiologists regarding the dispensing trends of Hearing Assistance Technology. Sixty-one responses were collected and analyzed revealing significant trends in HAT dispensing.