Aplicación del método de las DFDT a la simulación de dispositivos ópticos

[ES] La aplicación de las diferencias finitas en el dominio del tiempo (DFDT) para la simulación de dispositivos ópticos. En el rango de las longitudes de onda ópticas, la aplicación del método de las DFDT ha exigido un elevado coste computacional. La incorporación de distintas formulaciónes ha permitido la aplicación del algoritmo a sistemas ópticos.[EN] The aim of this work is to apply the difference time domain method for simulating optical devices. The wavelength used in optics makes harder the use of this algorithm in terms of time of processing. In this work different formalisms has been added such as near field to far field transformation, which has permitted to apply this algorithm to simulate optical devices like thin film filters and diffraction gratings. Satisfactory results has been achieved.The irradiance pattern obtained by the FDTD in far field (Fraunhofer region) is compared with analytical curves. Both curves are fit enough, as a result the algorithm has been validated. Rest of applications show the accuracy and potential of this algorithm applied to analyzing optical devices.Francés Monllor, J. (2009). Aplicación del método de las DFDT a la simulación de dispositivos ópticos. http://hdl.handle.net/10251/13049Archivo delegad

Evaluación del uso de dispositivos interactivos de respuesta (clickers) en Física Médica

La asignatura Bases Físicas de la Medicina se imparte durante el primer cuatrimestre primer curso de la Licenciatura en Medicina con una carga docente de 6 créditos. El docente, novedoso y acorde con el Espacio Europeo de Educación Superior (EEES) comienzo de la Facultad en 1998, pone al alumnado en el centro del proceso de enseñanza/aprendizaje. En este contexto, se han utilizado dispositivos personales de respuesta o clickers, no solo para incrementar la participación sino también para permitir alumnos evaluarse entre sí. En el presente trabajo se introducen sus principales aplicaciones, sugiriendo tácticas mejorar sus beneficios y optimizar su uso. También se detallan las primeras impresiones muy positivas de alumnos y profesores. Un total de 95 alumnos participaron en el estudio. 97,9% respondieron que los clickers habían hecho las sesiones más entretenidas, el consideraron que su uso les había ayudado a seguir mejor la clase, y el 87,4% creen participación se había incrementado. En cuanto a la evaluación de sus compañeros, el 45,3% trató de realizar calificaciones objetivas, el 31,6% siempre calificó con buenas notas independientemente de la calidad trabajo presentado. Después de algunas sesiones, el 17,9% demandó presentaciones y calificaron de manera más exigente y objetiva. Los alumnos sugirieron uso de los clickers en otras asignaturas con el fin de incrementar su motivación.Medical Physics is a four-month long subject taught during the first year of the degree in Medicine with a teaching load of 6 credits. The teaching method, new and in line with the European Higher Education Area (EHEA) since the beginning of the Faculty in 1998, puts the students at the center of teaching-learning process. In this context, we have used remote response devices or clickers, not only to increase the students participation but also to allow them to evaluate each other. In this paper we introduce its main applications, suggesting tactics to improve profits and optimize their use. It also details the very positive first impressions of students and teachers. A total of 95 students participated in the study. 97.9% responded that clickers had made the sessions most entertaining, 84.2% considered that their use had helped them to follow the class better, and 87.4% believe that their participation had increased. As for the evaluation of their classmates, 45.3% tried to make objective qualifications, 31.6% always scored good marks regardless of the quality of the submitted work. After a few sessions, 17.9% demanded better performances and marked in a more qualified and objective way. The students suggested the use of clickers in other subjects in order to increase their motivation

Performance analysis of SSE and AVX instructions in multi-core CPUs and GPU computing on FDTD scheme for solid and fluid vibration problems

In this work a unified treatment of solid and fluid vibration problems is developed by means of the Finite-Difference Time-Domain (FDTD). The scheme here proposed takes advantage from a scaling factor in the velocity fields that improves the performance of the method and the vibration analysis in heterogenous media. Moreover, the scheme has been extended in order to simulate both the propagation in porous media and the lossy solid materials. In order to accurately reproduce the interaction of fluids and solids in FDTD both time and spatial resolutions must be reduced compared with the set up used in acoustic FDTD problems. This aspect implies the use of bigger grids and hence more time and memory resources. For reducing the time simulation costs, FDTD code has been adapted in order to exploit the resources available in modern parallel architectures. For CPUs the implicit usage of the advanced vectorial extensions (AVX) in multi-core CPUs has been considered. In addition, the computation has been distributed along the different cores available by means of OpenMP directives. Graphic Processing Units have been also considered and the degree of improvement achieved by means of this parallel architecture has been compared with the highly-tuned CPU scheme by means of the relative speed up. The speed up obtained by the parallel versions implemented were up to 3 (AVX and OpenMP) and 40 (CUDA) times faster than the best sequential version for CPU that also uses OpenMP with auto-vectorization techniques, but non includes implicitely vectorial instructions. Results obtained with both parallel approaches demonstrate that massive parallel programming techniques are mandatory in solid-vibration problems with FDTD.The work is partially supported by the “Ministerio de Economía y Competitividad” of Spain under project FIS2011-29803-C02-01, by the Spanish Ministry of Education (TIN2012-34557), by the “Generalitat Valenciana” of Spain under projects PROMETEO/2011/021 and ISIC/2012/013, and by the “Universidad de Alicante” of Spain under project GRE12-14

Holographic Data Storage Using Parallel-Aligned Liquid Crystal on Silicon Displays

The parallel-aligned liquid crystal on silicon (PA-LCoS) microdisplay has become a widely used device for the photonics community. It is a very versatile tool that can perform several tasks which transforms it into a key element in many different photonics applications. Since our group is interested in holography, in this chapter, we want to use these displays as the data entry point for a holographic data storage system (HDSS). Due to the novelty of this kind of device, we have done an intense work characterizing it. These efforts are reflected in this chapter where the reader will find two different characterization methods that will enable to predict the performance of the device in a specific application. Additionally, we present how a phase-only device can be used as a data pager using different modulation schemes and combined with a photopolymer as the holographic recording material

Implementación de métodos numéricos para el análisis electromagnético de medios periódicos: aplicación en longitudes de onda ópticas y optimización computacional

En esta tesis doctoral se ha desarrollado una serie de métodos numéricos para el análisis de dispositivos ópticos difractivos. Los dispositivos ópticos difractivos básicamente consisten en medios cuyas características físicas varían de forma periódica. Las aplicaciones de este tipo de elementos son diversas y parten desde filtros ópticos, fabricación de lentes, redes de difracción holográficas hasta aplicaciones de energía solar fotovoltaica. En particular, en esta Tesis Doctoral, se han analizado redes de difraccion holográficas de volumen (tanto en reflexión como en transmisión), redes de difracción basadas en aperturas, así como filtros dieléctricos de capas delgadas. Para el análisis riguroso y completo de estos medios en longitudes de onda ópticas se ha recurrido al método de las Diferencias Finitas en el Dominio del Tiempo (DFDT), el cual permite resolver las ecuaciones de Maxwell que modelan el campo electromagnético, en función del tiempo y del espacio. El estudio mediante el método numérico de las DFDT ha sido contrastado con las teorías clásicas que modelan el comportamiento de estos dispositivos, obteniendo resultados satisfactorios. La aplicación del método de las DFDT en longitudes de onda ópticas implica unas resoluciones temporales y espaciales muy reducidas, por lo que la simulación de mallas de varios órdenes de magnitud de la longitud de onda de trabajo repercute en un aumento del coste computacional y de memoria. Por ello, este método se ha acelarado mediante diferentes técnicas con el propósito de obtener el mayor rendimiento posible en las plataformas de cálculo más comunes en la actualidad: Unidades de Proceso Central (UPC) disponibles en los microprocesadores modernos, y Unidades de Procesado Gráfico (UPG) las cuales están presentes en las tarjetas gráficas de los computadores actuales

Vibro-acoustic behavior of Spanish bells with metallic and wooden yoke

With the purpose of studying the acoustics of the same bell with wooden yoke and with metallic yoke, a bell to which have been installed both yokes has settled in the acoustically conditioned room of the University of Alicante and acoustic experiences have been carried out for separate for each one of them. A Test protocol has been defined selecting points located in different quadrants and at different heights on the brass was hit with a hammer impact. The bell response has registered with a microphone and analyzed to permit compare under laboratory conditions the frequency response of oneself bell with two types of different yokes

Introducción a la Investigación en Telecomunicación (Guía de la asignatura)

La asignatura presenta una serie de conceptos fundamentales sobre la investigación científica y su metodología. Se abordan aspectos sobre los proyectos de investigación, las publicaciones y la presentación de los resultados de investigación en los foros de discusión científica

Interference and diffraction analysis of holographic gratings using the Finite-Difference Time-Domain method

The Finite-Difference Time-Domain method (FDTD) is based on a time-marching algorithm that has proven accurate in predicting microwave scattering from complicated objects. In this work the method is applied at optical wavelengths, more concretely the method is applied to rigorously analyze holographic gratings for the near-field distribution. It is well known that diffraction gratings with feature sizes comparable to the wavelength of light must be treated electromagnetically, because the scalar diffraction theories, including Fourier and Fresnel approximations, no longer apply. The FDTD method permits to analyze the electromagnetic field distribution in function of time and space. In optical wavelenghts the simulation of wide areas implies more memory and time processing. For that reason, some add-ons are included in order to correctly calculate the far field distribution obtained from the numerical near-field values computed in the simulation region. As a consequence the total grid simulation size can be reduced improving the performance of the simulation, in terms of memory usage and time processing. Values in the near-field region are computed due to the illumination of the grating by means of a plane wave with different angle of incidence. In addition, we compare the results obtained by the FDTD method to those obtained using the Kogelnik's theoretical expressions applied to diffraction gratings. As it will be seen in this work there is good agreement between numerical and analytical values, thus validating our FDTD implementation.This work was supported by the Ministerio Ciencia e Innovación of Spain under project FIS2008-05856-C02-02 and by the ”Generalitat Valenciana” of Spain under project ACOMP/2010/156

Rigorous interference and diffraction analysis of diffractive optic elements using the finite-difference time-domain method

The Finite-Difference Time-Domain (FDTD) method has proven to be a useful tool to analyze electromagnetic scattering phenomena. In this work, the FDTD method is applied at optical wavelengths. More precisely, we present the results obtained using the FDTD algorithm to simulate the performance of optical devices such as volume diffraction gratings. The Perfectly Matched Layers (PML), Total-Field Scattered-Field formulation (TF/SF) and Near-Field to Far-Field transformation (NF/FF) are some add-ons included in order to correctly calculate the far field distribution obtained from the numerical near-field values computed in the simulation region. These values in the near-field region are computed by illuminating the grating with of a plane wave at the Bragg angle of incidence. In addition, we compare the results obtained by the FDTD method to those obtained using the Rigorous Coupled Wave Theory (RCWT) applied to diffraction gratings. As will be seen in this paper there is good agreement between the two approaches, thus validating our FDTD implementation.This work was supported by the “Ministerio Ciencia e Innovación” of Spain under project FIS2008-05856-C02-02, by the “Generalitat Valenciana” of Spain under project ACOMP/2010/156 and by the University of Alicante under the project GRE09-10

University Physics Education using Facebook

The European Space for Higher Education, pushed by the Bologna process, demands a change in the way the courses in the University are taught. This has resulted in an increased importance being placed on individual work that the students do, but it should be always supervised and directed by the teacher. The supervision is generally carried out through three main ways: attended sessions, work in groups and that done at home. To cover all these new issues and needs many universities are applying a tool for e-Learning called Campus Virtual which is based on Moodle. This tool of exchanging information allows the teacher to offer resources of the subject that they teach and works as a communication path using messages and forums, as well as receiving reports done by the students, group assignments, etc. Nevertheless this tool can be limited in terms of flexibility and accessibility as the tutoring, in cases where a lot of self-learning is needed, requires communications to be fast, flexible and easy. In this scenario the social networks offer new possibilities. We analyse the activity and satisfaction of various teaching groups on Facebook in different courses of the following degrees in the UCLM: Computer Science Engineering and Medicine. The results obtained during the first semester show a high level of participation and frequent access, as well as, good general acceptance and use of the information provided by both students and teachers. Our intention is to promote and extend the use of these social networks to groups with which we collaborate both at the University of Alicante and at the Advanced Technology, National Polytechnic Institute of Mexico, to be able to compare the results of different populations of students. The use of student groups on Facebook represents a new way for the direct and rapid transfer of information that has been accepted and evaluated differently. The students are quite receptive of its use, as it is much more user-friendly than Moodle, which from the beginning students perceive as exclusively academic, associated with work and evaluation, and so it results less attractive to many of them and therefore is harder for the students to be an active part of. In fact for the teacher it is very complicated to create an active communication forum in Moodle, while in the groups created on Facebook the participation rate is quite high. This is due to the students being familiarized with these social networks and also with the enthusiasm of the teacher and the content of the information exchanged. However the use of Facebook by the teachers is not as common as desired, maybe because it means a duplication of effort and resources (putting the same information in two different places), which require more time being invested on the subject, even though it provides improved communications with the students. It is also worth mentioning that it can be a place to meet and exchange opinions and comments between the students and the faculty, enriching their self-learning, critical thinking, relationships, etc.Part of this work was financed by the Vice-rectorate of Technology and Educational Innovation of the University of Alicante (Spain), under project GITE-09006-UA