Modelización de dispositivos optoelectrónicos microestructurados. Métodos modales

RESUMEN En esta tesis se ha desarrollado un método de representación modal tridimensional para la obtención del espectro de modos de cavidades inhomogéneas. El método se fundamenta en el hecho de que los modos de una cavidad inhomogénea son solución de una ecuación de valores propios, cuyo operador es autoadjunto. Con ello, la solución de un problema auxiliar sencillo puede proporcionar una base ortogonal para representar matricialmente las ecuaciones diferenciales de otros problemas de mayor complejidad. De esta forma, el problema se reduce a la solución de un sistema algebraico de valores propios. El método propuesto permite calcular los modos de sistemas inhomogéneos con distribuciones arbitrarias del índice de refracción. Estos sistemas pueden ser abiertos o cerrados, incluso pueden incluir medios absorbentes cuyos índices de refracción sean complejos. La validez del método se ha comprobado analizando diferentes sistemas, tanto en el rango óptico (láminas de cristal fotónico) como en el de las microondas (cavidades inhomogéneas), y comparando los resultados obtenidos con los publicados anteriormente por diferentes autores. Esto ha servido para tratar las cuestiones prácticas que surgen en la implementación del método, como son el efecto de una frontera artificial en el estudio de sistemas abiertos y el efecto del número finito de modos de la base auxiliar. El método desarrollado se caracteriza por su generalidad y una alta versatilidad para tratar problemas no convencionales, lo que se ha aprovechado para estudiar láminas de cristal fotónico en las que las paredes de los surcos están inclinadas, sistema que no puede ser simulado ―o es prácticamente inviable su análisis― mediante otras técnicas más convencionales. En una segunda parte, se ha particularizado el método modal tridimensional al caso bidimensional y reobteniendo el método modal de las bases biortogonales desarrollado con anterioridad en la Universitat de València. Este método modal bidimensional se ha empleado para estudiar algunas guías que soportan los llamados modos complejos, cuyas constantes de propagación presentan una parte imaginaria aunque no hayan pérdidas en los materiales. Con este método se han obtenido, también, los modos de estructuras guiadoras complejas como son las fibras de Bragg, identificando diferentes diseños para los que la dispersión de la velocidad de grupo de estas fibras posee un comportamiento acromático o apocromático, con dispersión positiva, negativa o nula, en diferentes ventanas de longitudes de ondas. Finalmente, se ha abordado el estudio de las propiedades de transmisión y reflexión de dispositivos inhomogéneos con guías de entrada y salida también inhomogéneas. Para ello, se ha combinado adecuadamente los métodos de representación modal tridimensional y bidimensional con el desarrollo de una nueva técnica para la determinación de los parámetros de scattering de los dispositivos. Como aplicación inmediata de esta técnica, se han analizado, por un lado, el comportamiento de algunos filtros y adaptadores basados en guías NRD de microondas, y por otro, la respuesta de filtros ópticos y microcavidades construidos con láminas de cristal fotónico unidimensionales de tamaño finito y con defectos. __________________________________________________________________________________________________In this doctoral thesis a novel modal method has been formulated to analyse three dimensional dielectric systems. The vector wave equation which determines the resonant frequencies and fields is written in terms of a linear operator, whose eigenvectors satisfy a orthonormality relation. The key of the method is to obtain a matrix representation of the wave equation in a basis that is defined by the modes of an auxiliary system. The method has been applied to study optical devices (photonic crystal waveguides) and microwave cavities. The accuracy of the method is demonstrated by comparing the obtained results with other results available in the literature. In a second part, the technique has been particularised to analyse translation invariant systems reobtaining the biorthogonal-basis method. This method has been used to model the complex wave propagation in inhomogeneously filled waveguides and the group velocity dispersion properties of a novel type of Bragg fibres. Finally, a computationally efficient technique has been developed for the full-wave characterisation of inhomogeneously dielectric-filled cavities connected to inhomogeneously dielectric loaded waveguides. The multimode scattering matrix of the cavity is computed throughout an efficient implementation of the orthonormal-basis method for the calculation of the cavity modes. Moreover, the biorthogonal-basis method is employed for the analysis of the waveguides connected to the cavity. Non-radiative dielectric guide components and microstructured optoelectronic devices generated with photonic crystal waveguides have been analysed using the present technique

Experimental characterisation of the motion of an inverted pendulum

[EN] : In this paper, we present a home-made experimental set-up to study the falling movement of an inverted pendulum. The experimental set-up allows preparing a laboratory session for first year Physics or Engineering students. This set-up has been used in the Bachelor's Degree in Mechanical Engineering at the School of Design Engineering of the Universitat Politècnica de València. The experimental data are fitted to the theoretical equation of motion, obtaining a very good agreement between experiment and theory. In addition, direct measurement of the parameters involved in the equations was carried out, showing a very good agreement with the calculated parameters.Gómez Tejedor, JA.; Mollar, M.; Monsoriu Serra, JA. (2015). Experimental characterisation of the motion of an inverted pendulum. En 1ST INTERNATIONAL CONFERENCE ON HIGHER EDUCATION ADVANCES (HEAD' 15). Editorial Universitat Politècnica de València. 588-592. https://doi.org/10.4995/HEAD15.2015.331OCS58859

Direct measurement of the speed of sound using a microphone and a speaker

[EN] We present a simple and accurate experiment to obtain the speed of sound in air using a conventional speaker and a microphone connected to a computer. A free open source digital audio editor and recording computer software application allows determination of the timeofflight of the wave for different distances, from which the speed of sound is calculated. The result is in very good agreement with the reported value in the literature.The authors would like to thank the Institute of Education Sciences, Universitat Politecnica de Valencia (Spain), for the support of the Teaching ` Innovation Groups, MoMa and e-MACAFI.Gómez-Tejedor, JA.; Castro Palacio, JC.; Monsoriu Serra, JA. (2014). Direct measurement of the speed of sound using a microphone and a speaker. Physics Education. 49(3):310-313. doi:10.1088/0031-9120/49/3/310310313493LoPresto, M. C. (2011). Experimenting with end-correction and the speed of sound. Physics Education, 46(4), 437-439. doi:10.1088/0031-9120/46/4/011Ng, Y., & Mak, S. (2000). Measurement of the speed of sound in water. Physics Education, 36(1), 65-70. doi:10.1088/0031-9120/36/1/312Mak, S., Ng, Y., & Wu, K. (2000). Measurement of the speed of sound in a metal rod. Physics Education, 35(6), 439-445. doi:10.1088/0031-9120/35/6/311Albergotti, J. C. (1981). Speed of sound by a time‐of‐flight method. American Journal of Physics, 49(6), 595-596. doi:10.1119/1.12466Ouseph, P. J., & Link, J. J. (1984). Variation of speed of sound in air with temperature. American Journal of Physics, 52(7), 661-661. doi:10.1119/1.1387

Influencia de los diferentes tipos de astigmatismo en la agudeza visual

[EN] Purpose To investigate the change in visual acuity (VA) produced by different types of astigmatism (on the basis of the refractive power and position of the principal meridians) on normal accommodating eyes. Methods The lens induced method was employed to simulate a set of 28 astigmatic blur conditions on different healthy emmetropic eyes. Additionally, 24 values of spherical defocus were also simulated on the same eyes for comparison. VA was measured in each case and the results, expressed in logMAR units, were represented against of the modulus of the dioptric power vector (blur strength). Results LogMAR VA varies in a linear fashion with increasing astigmatic blur, being the slope of the line dependent on the accommodative demand in each type of astigmatism. However, in each case, we found no statistically significant differences between the three axes investigated (0°, 45°, 90°). Non-statistically significant differences were found either for the VA achieved with spherical myopic defocus (MD) and mixed astigmatism (MA). VA with simple hyperopic astigmatism (SHA) was higher than with simple myopic astigmatism (SMA), however, in this case non conclusive results were obtained in terms of statistical significance. The VA achieved with imposed compound hyperopic astigmatism (CHA) was highly influenced by the eye's accommodative response. Conclusions VA is correlated with the blur strength in a different way for each type of astigmatism, depending on the accommodative demand. VA is better when one of the focal lines lie on the retina irrespective of the axis orientation; accommodation favors this situation.[ES] Objetivo Investigar el cambio en la agudeza visual (AV) producido por los diferentes tipos de astigmatismo (sobre la base del poder refractivo y la posición de los principales meridianos) en ojos con acomodación normal. Métodos Se utilizó el método de desenfoque inducido con lentes para simular un conjunto de veintiocho situaciones de desenfoque astigmático en diferentes ojos emetrópicos sanos. Además, se simularon veinticuatro valores de defecto esférico en los mismos ojos, a fines comparativos. Se midió la AV en cada caso, representándose los resultados, expresados en unidades logMAR, frente a los módulos del vector de potencia dióptrica (desenfoque). Resultados La escala LogMAR para AV varía de manera lineal, incrementando la distorsión astigmática, dependiendo la inclinación de la línea de la demanda acomodativa en cada tipo de astigmatismo. Sin embargo, en cada caso, no hallamos diferencias significativas entre los tres ejes analizados (0°, 45°, 90°). No se hallaron diferencias estadísticamente significativas en cuanto a la AV lograda con el defecto miópico esférico (MD) y astigmatismo mixto (MA). La AV con astigmatismo hipermetrópico simple (SHA) fue más elevada que con astigmatismo miópico simple (SMA). Sin embargo, en este caso se obtuvieron resultados no concluyentes en términos de significancia estadística. La AV lograda con astigmatismo hipermetrópico compuesto (CHA) se vio altamente influenciada por la respuesta acomodativa del ojo. Conclusiones La AV guarda relación con el desenfoque de modo diferente para cada tipo de astigmatismo, dependiendo de la demanda de acomodación. La AV es mejor cuando una de las líneas focales está en la retina con independencia de la orientación del eje; la acomodación favorece esta situación.This study was supported by the Ministerio de Economía y Competitividad and FEDER (Grant DPI2015-71256-R), and by the Generalitat Valenciana (Grant PROMETEOII-2014-072), Spain.Remón Martín, L.; Monsoriu Serra, JA.; Furlan, WD. (2017). Influence of different types of astigmatism on visual acuity. Journal of Optometry. 10(3):141-148. https://doi.org/10.1016/j.optom.2016.07.003S14114810

Diseño y desarrollo de un espectrómetro óptico versátil de bajo coste

[EN] In this work, the processes of designing, developing and prototyping an instrument to measure the visible spectrum is shown in detail. The objective is to obtain a low-cost device, reproducible and technically competitive with the commercial docent models. The obtained device is portable, adaptable, compact, economic and with high connectivity. The core of the project is the software, and its key point is the compatibility with any commercial camera and it can be run in different operative systems. For this prototype a commercial camera with USB connection has been considered in order to find a balance between price and resolution for the resulting device.[ES] En este trabajo se detalla el proceso de diseño, desarrollo y prototipado de un sistema de medida del espectro visible. El objetivo que hay que cumplir es la obtención de un dispositivo reproducible, competitivo en el aspecto técnico con modelos comerciales de docencia actuales, y económico. El dispositivo resultante reúne las características de ser portátil, versátil, compacto, económico y con alta conectividad. El centro del proyecto es el software, que como característica clave permite ser utilizado prácticamente con cualquier cámara comercial y ser ejecutado desde distintos sistemas operativos. El prototipado se ha realizado con una cámara comercial con conexión USB con el fin de encontrar un equilibrio entre asequibilidad y resolución del producto final. Tiene un precio 20 veces más económico y una resolución similar al espectrofotómetro comercial utilizado como referencia.Este trabajo ha sido financiado por el Ministerio de Economía y Competitividad y FEDER (Proyecto DPI2015-71256-R) y por la Generalitat Valenciana (Proyecto PROMETEOII-2014-072).Ferrando, V.; Monreal, J.; Furlan, WD.; Monsoriu Serra, JA. (2017). Diseño y desarrollo de un espectrómetro óptico versátil de bajo coste. Tecnica Industrial. (318):48-52. https://doi.org/10.23800/9984S485231

Guiding properties of a photonic quasi-crystal fiber based on the thue-morse sequence

© 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.We present a novel microstructured optical fiber having a quasi-periodic distribution of air holes based on the Thue–Morse sequence. The transverse section of these fibers is basically a two-dimensional photonic quasi-crystal that can also provide complete photonic bandgaps without being a perfect periodic structure. Like in the conventional photonic crystal fibers, if the quasi-periodicity is broken by decreasing the size of some air holes or by introducing an extra air hole, the modified holes become defects that localize and guide light along the fiber. The guidance is attributed to the inhibition of transverse radiation produced by the photonic quasi-crystal cladding. Dispersion curves of guided modes for different structural parameters are calculated, along with the transverse intensity distribution of the fundamental mode. In particular, several specially designed Thue–Morse quasi-crystal fibers with nearly zero ultraflattened group-velocity dispersion are presented.This work was supported in part by the Generalitat Valenciana, Spain, under Grant ACOMP/2014/180 and Grant PROMETEOII/2014/072, and in part by the Ministerio de Economia y Competitividad under Grant FIS2011-23175 and Grant TEC2013-46643-C2-1-R. (Corresponding author: Juan A. Monsoriu.)Ferrando Martín, V.; Coves, Á.; Andrés, P.; Monsoriu Serra, JA. (2015). Guiding properties of a photonic quasi-crystal fiber based on the thue-morse sequence. IEEE Photonics Technology Letters. 27(18):1903-1906. https://doi.org/10.1109/LPT.2015.2444991S19031906271

Proposal of a new diffractive corneal inlay to improve near vision in a presbyopic eye

[EN] A new class of diffraction-based corneal inlays for treatment of presbyopia is described. The inlay is intended to achieve an improvement of the near focus quality over previous designs. Our proposal is a two-zone hybrid device with separated amplitude and phase areas having a central aperture and no refractive power. An array of micro-holes is distributed on the surface of the inlay conforming a binary photon sieve. In this way, the central hole of the disk contributes to the zero order of diffraction, and the light diffracted by the micro-holes in the peripheral photon sieve produces a real focus for near vision. We employed ray-tracing software to study the performance of the new inlay in the Liou-Brennan model eye. The modulation transfer functions (MTFs) at the distance and near foci, and the area under the MTFs for different object vergences, were the merit functions used in the evaluation. The results were compared with those obtained with previous pure amplitude designs. Additionally, image simulations were performed with the inlays in the model eye to show the good performance of our proposal in improving the quality of the near vision. (C) 2020 Optical Society of AmericaMinisterio de Economia y Competitividad, Spain (2019/048, DPI 2015-71256-R); Conselleria d'Educacio, Investigacio, Cultura i Esport, Comunitat Valenciana, Spain (PROMETEO/2019/048). Portions of this work were presented at the Optics Meeting (RIAO), the Latinoamerican Meeting in Optics, Lasers and Applications (OPTILAS), and the Mexican Optics and Photonics Meeting (MOPM) in September 2019, Diffractive corneal inlays: ray tracing analysis in a model eye . D. Montagud Martinez and V. Ferrando acknowledge the financial support from the Universitat Politècnica de València, Spain (fellowships FPI 2016 and PAID 10 18, respectively).Montagud-Martínez, D.; Ferrando, V.; Monsoriu Serra, JA.; Furlan, WD. (2020). Proposal of a new diffractive corneal inlay to improve near vision in a presbyopic eye. Applied Optics. 59(13):D54-D58. https://doi.org/10.1364/AO.383581SD54D585913Lindstrom, R. L., MacRae, S. M., Pepose, J. S., & Hoopes, P. C. (2013). Corneal inlays for presbyopia correction. Current Opinion in Ophthalmology, 24(4), 281-287. doi:10.1097/icu.0b013e328362293eCharman, W. N. (2014). Developments in the correction of presbyopia II: surgical approaches. Ophthalmic and Physiological Optics, 34(4), 397-426. doi:10.1111/opo.12129Furlan, W. D., García-Delpech, S., Udaondo, P., Remón, L., Ferrando, V., & Monsoriu, J. A. (2017). Diffractive corneal inlay for presbyopia. Journal of Biophotonics, 10(9), 1110-1114. doi:10.1002/jbio.201600320Kipp, L., Skibowski, M., Johnson, R. L., Berndt, R., Adelung, R., Harm, S., & Seemann, R. (2001). Sharper images by focusing soft X-rays with photon sieves. Nature, 414(6860), 184-188. doi:10.1038/35102526Giménez, F., Monsoriu, J. A., Furlan, W. D., & Pons, A. (2006). Fractal photon sieve. Optics Express, 14(25), 11958. doi:10.1364/oe.14.011958Montagud-Martinez, D., Ferrando, V., Machado, F., Monsoriu, J. A., & Furlan, W. D. (2019). Imaging Performance of a Diffractive Corneal Inlay for Presbyopia in a Model Eye. IEEE Access, 7, 163933-163938. doi:10.1109/access.2019.2949223Montagud-Martínez, D., Ferrando, V., Monsoriu, J. A., & Furlan, W. D. (2019). Optical Evaluation of New Designs of Multifocal Diffractive Corneal Inlays. Journal of Ophthalmology, 2019, 1-6. doi:10.1155/2019/9382467Liou, H.-L., & Brennan, N. A. (1997). Anatomically accurate, finite model eye for optical modeling. Journal of the Optical Society of America A, 14(8), 1684. doi:10.1364/josaa.14.001684Alarcon, A., Canovas, C., Rosen, R., Weeber, H., Tsai, L., Hileman, K., & Piers, P. (2016). Preclinical metrics to predict through-focus visual acuity for pseudophakic patients. Biomedical Optics Express, 7(5), 1877. doi:10.1364/boe.7.00187

Frequency Analyzer: a new teaching app for Android

[EN] In this paper we present an application for Android mobile device able of measuring the fundamental frequency of a sound very precisely. This application may be used in diverse fields as in music for tuning musical instruments, in physics for measuring the Doppler effect or in speech recognition systems to determine the fundamental frequency of the voice. Specifically, in this paper we present some examples in the field of physics related to the Doppler effect for sound waves[ES] En este trabajo se presenta una aplicación para dispositivo móvil Android capaz de medir la frecuencia fundamental de un sonido de forma muy precisa. Esta aplicación puede ser utilizada en campos tan diversos como la música para afinar instrumentos musicales, en física para la medida del efecto Doppler o en sistemas de reconocimiento del habla para determinar la frecuencia fundamental de la voz. En concreto, en este trabajo presentamos algunos ejemplos en el campo de la física relacionados con el efecto Doppler para ondas acústicas.Gómez-Tejedor, JA.; Monsoriu Serra, JA. (2014). Analizador de Frecuencia: una nueva aplicación docente para Android. Modelling in Science Education and Learning. 7:17-24. doi:10.4995/msel.2014.2085SWORD17247Baker, B. (2005). Dozen: Real analog solutions for digital designers. Burlington, Massachusetts: Elsevier.Butterworth, S. (1930). On the theory of filter amplifiers. Experimental Wireless and the Wireless Engineer, 7, 536–541.Cramer, O. (1993). The variation of the specific heat ratio and the speed of sound in air with temperature, pressure, humidity, and CO2 concentration. The Journal of the Acoustical Society of America, 93(5), 2510-2516. doi:10.1121/1.405827Doppler, C. (1842). Uber das farbige licht der doppelsterne und einiger anderer gestirne des himmels. Abhand-lungen der k. b ̈hm. Gesellschaft der Wissenschaften, 2, 465-482.Tipler, P. A., & Mosca, G. (2008). Physics for scientists and engineers. New York: W.H. Freeman and Company

Optical Evaluation of New Designs of Multifocal Diffractive Corneal Inlays

[EN] Purpose. To assess the imaging properties of two different designs of a new concept of corneal inlays whose working principle is based on diffraction. Methods. The quality of the retinal images provided by Diffractive Corneal Inlays (DCIs) was evaluated theoretically in comparison with Small Aperture Corneal Inlay (SACI). ZEMAX OpticStudio software was employed for the simulations in an eye model with different pupil diameters (3.0 mm and 4.5 mm). The employed merit functions in the analysis were the Modulation Transfer Function (MTF), the area under the MTF (MTFa), and the Point Spread Function (PSF). Comparison was made with the SACI at different defocus conditions. Results. The bifocal nature of the DCIs was demonstrated in a model eye for the first time. It was shown that the intensity of the near focus depends on the radius of the central zone. Retinal image quality of the DCI was equal to or exceeded the SACI in the majority of visual conditions as was demonstrated with simulated images. Conclusions. A new customizable type of corneal inlays has been evaluated using objective numerical simulations. Improvements in imaging of near objects and in light throughput compared with the popular small aperture inlays were demonstrated. These findings open a new technical branch of minimally invasive surgical solutions for the treatment of presbyopia.D. Montagud-Martinez and V. Ferrando acknowledge the financial support from the Universitat Politècnica de València, Spain (fellowships FPI-2016 and PAID-10-18, respectively). This work was supported in part by the Ministerio de Economia y Competitividad, Spain, (grant DPI2015-71256-R) and by the Generalitat Valenciana (Grant PROMETEO/2019/048), Spain.Montagud-Martínez, D.; Ferrando, V.; Monsoriu Serra, JA.; Furlan, WD. (2019). Optical Evaluation of New Designs of Multifocal Diffractive Corneal Inlays. Journal of Ophthalmology. 2019:1-6. https://doi.org/10.1155/2019/9382467S162019Fricke, T. R., Tahhan, N., Resnikoff, S., Papas, E., Burnett, A., Ho, S. M., … Naidoo, K. S. (2018). Global Prevalence of Presbyopia and Vision Impairment from Uncorrected Presbyopia. Ophthalmology, 125(10), 1492-1499. doi:10.1016/j.ophtha.2018.04.013Furlan, W. D., García-Delpech, S., Udaondo, P., Remón, L., Ferrando, V., & Monsoriu, J. A. (2017). Diffractive corneal inlay for presbyopia. Journal of Biophotonics, 10(9), 1110-1114. doi:10.1002/jbio.201600320Kipp, L., Skibowski, M., Johnson, R. L., Berndt, R., Adelung, R., Harm, S., & Seemann, R. (2001). Sharper images by focusing soft X-rays with photon sieves. Nature, 414(6860), 184-188. doi:10.1038/3510252

Fundamentos Físicos de la Óptica de Multicapas

Cuando una onda plana llega a la superficie de separación de dos medios homogéneos con diferentes índices de refracción da lugar a una onda transmitida en el segundo medio y una onda reflejada en el primer medio. Se estudiarán las relaciones entre las amplitudes (coeficientes de reflexión y transmisión) e intensidades (reflectancia y transmitancia) de las ondas obteniendo las expresiones conocidas como fórmulas de Fresnel. Se abordará el estudio de las películas delgadas monocapa y multicapa que se utilizan en diversas aplicaciones físicas. Se introducirá un método matricial que aborda de modo más sencillo y sistemático el estudio de las películas multicapa.AMPARO PONS MARTI; Monsoriu Serra, JA.; Ferrando, V. (2021). Fundamentos Físicos de la Óptica de Multicapas. Escuela Técnica Superior de Ingeniería del Diseño. http://hdl.handle.net/10251/165249