Person: López Alonso, José Manuel
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First Name
José Manuel
Last Name
López Alonso
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Óptica y Optometría
Department
Óptica
Area
Optica
Identifiers
15 results
Search Results
Now showing 1 - 10 of 15
Item Multivariate analysis of photonic crystal microcavities with fabrication defects(Photonic Materials, Devices, and Applications, Pts 1 and 2, 2005) Rico García, José María; López Alonso, José Manuel; Alda Serrano, JavierPhotonic crystal microcavities are defined by the spatial arrangement of materials. In the analysis of their spatial temporal mode distributions Finite-Difference Time-Domain (FDTD) methods have proved its validity. The output of the FDTD can be seen as the realizations of a multidimensional statistic variable. At the same time, fabrication tolerances induce an added and unavoidable variability in the performance of the microcavity. In this contribution we have analyzed the modes of a defective photonic crystal microcavity. The location, size, and shape of the cylinders configuring the microcavity are modelled as having a normal distribution of their parametric descriptors. A principal component analysis is applied to the output of the FDTD for a population of defective microcavities. The relative importance of the defects is evaluated, along with the changes induced in the spatial temporal distribution of electromagnetic field obtained from the calculation.Item Characterization of spatial–temporal patterns in dynamic speckle sequences using principal component analysis(Optical Engineering, 2016) López Alonso, José Manuel; Grumel, Eduardo; Cap, Nelly Lucía; Trivi, Marcelo; Rabal, Héctor; Alda Serrano, JavierAbstract. Speckle is being used as a characterization tool for the analysis of the dynamics of slow-varying phenomena occurring in biological and industrial samples at the surface or near-surface regions. The retrieved data take the form of a sequence of speckle images. These images contain information about the inner dynamics of the biological or physical process taking place in the sample. Principal component analysis (PCA) is able to split the original data set into a collection of classes. These classes are related to processes showing different dynamics. In addition, statistical descriptors of speckle images are used to retrieve information on the characteristics of the sample. These statistical descriptors can be calculated in almost real time and provide a fast monitoring of the sample. On the other hand, PCA requires a longer computation time, but the results contain more information related to spatial–temporal patterns associated to the process under analysis. This contribution merges both descriptions and uses PCA as a preprocessing tool to obtain a collection of filtered images, where statistical descriptors are evaluated on each of them. The method applies to slow-varying biological and industrial processes.Item Principal-component characterization of noise for infrared images(Applied Optics, 2002) López Alonso, José Manuel; Alda, Javier; Bernabeu Martínez, EusebioPrincipal-component decomposition is applied to the analysis of noise for infrared images. It provides a set of eigenimages, the principal components, that represents spatial patterns associated with different types of noise. We provide a method to classify the principal components into processes that explain a given amount of the variance of the images under analysis. Each process can reconstruct the set of data, thus allowing a calculation of the weight of the given process in the total noise. The method is successfully applied to an actual set of infrared images. The extension of the method to images in the visible spectrum is possible and would provide similar results.Item Antenas ópticas y detectores de luz(Ver y Oír, 2005) Alda Serrano, Javier; López Alonso, José Manuel; Boreman, Glenn; Rico García, José MaríaLa investigación sobre el comportamiento de estructuras metálicas cuyo tamaño es comparable a la longitud de onda de la radiación detectada puede realizarse considerándolas como antenas detectoras de radiación óptica. El diseño, análisis y caracterización de estos dispositivos requiere el estudio de los fenómenos básicos de interacción entre la radiación y la materia. A la vez, su inclusión en sistemas con relevancia tecnológica requiere la medida y caracterización de sus propiedades. Nuestro equipo de investigación, integrado en el «Grupo Complutense de Óptica Aplicada», se ha dedicado durante los últimos años al estudio de estos dispositivos así como a la caracterización de todo tipo de detectores de luz, y a la definición de aquellas figuras de mérito que son relevantes a la hora de establecer su uso.Item Principal Component Analysis of Results Obtained from Finite-Difference Time-Domain Algorithms(Egyptian Journal of Solids, 2006) López Alonso, José Manuel; Rico García, José María; Alda Serrano, JavierFinite-Differences Time-Domain (FDTD) algorithms are well established tools of computational electromagnetism. Because of their practical implementation as computer codes, they are affected by many numerical artefact and noise. In order to obtain better results we propose using Principal Component Analysis (PCA) based on multivariate statistical techniques. The PCA has been successfully used for the analysis of noise and spatial temporal structure in a sequence of images. It allows a straightforward discrimination between the numerical noise and the actual electromagnetic variables, and the quantitative estimation of their respective contributions. Besides, The GDTD results can be filtered to clean the effect of the noise. In this contribution we will show how the method can be applied to several FDTD simulations: the propagation of a pulse in vacuum, the analysis of two-dimensional photonic crystals. In this last case, PCA has revealed hidden electromagnetic structures related to actual modes of the photonic crystal.Item FDTD analysis of nano-antenna structures with dispersive materials at optical frequencies(Nanotechnology II. Proceedings of the Society of Photo-Optical Instrumentation Engineers, 2005) Rico García, José María; López Alonso, José Manuel; Alda Serrano, JavierThe Finite-Difference Time Domain method has encountered several difficulties when analyzing dispersive materials. This is the case of the metal structures that configure an optical antenna. These devices couple the electromagnetic radiation to conform currents that are rectified by another physical element attached to the antenna. Both elements: antenna and rectifier configures an optical detector with sub-wavelength dimensions. In this contribution we analyze the effect on the currents induced by the incident electromagnetic field using FDTD and taking into account the dispersive character of metal at optical frequencies. The analysis is done in a 2 dimensional framework and it serves as an analytical tool for the election of material and structures in the fabrication of optical antennas.Item Micro- and Nano-Antennas for Light Detection(Egyptian Journal of Solids, 2005) Alda Serrano, Javier; Rico García, José María; López Alonso, José Manuel; Boreman, GlennAntenna-coupled optical detectors, also named as optical antennas, are being developed as detection devices with micro- and nano-scale features for their use in the millimetre, infrared, and visible spectral range. They are optical components that couple the electromagnetic radiation in the visible and infrared wavelengths in the same way that radioelectric antennas do at the corresponding wavelengths. Optical antennas show polarization dependence, tuneability, and rapid time of response. They also can be considered as point detectors and directionally sensitive elements. So far, these detectors have been operated in the mid-infrared with positive results in the visible. The measurement and characterization of optical antennas requires the use of an experimental set-up with nanometric resolution. On the other hand, a computational simulation of the interaction between the material structures and the incoming electromagnetic radiation is needed to explore alternative designs of practical devices. In this contribution we will present the concept of optical and infrared antennas, and some experimental results of their performance, along with the experimental set-up arranged for their characterization in the visibleItem High-resolution spatial-response measurements of optical nano-antennas in the visible(IEEE Antennas and Propagation Society International Symposium, IEEE Antennas and Propagation Society International Symposium, 2007) Alda Serrano, Javier; Rico García, José María; López Alonso, José Manuel; Boreman, GlennA few years ago, some of the authors of the paper demonstrated the resonance of optical antennas in the visible frequencies. The results of that paper were obtained using experimental techniques that were primarily developed for the measurement of antenna-coupled detectors in the infrared. In the present paper, we show the results of spatial-response mapping obtained by using a dedicated measurement station for the characterization of optical antennas in the visible. At the same time, the bottleneck in the spatial responsivity calculation represented by the beam characterization has been approached from a different perspective. The proposed technique uses a collection of knife edge measurements in order to avoid the use of any model of the laser beam irradiance. By taking all this into account we present the spatial responsivity of optical antennas measured with high spatial resolution in the visible.Item Characterization of photonic crystal microcavities with manufacture imperfections(Optics Express, 2005) Rico García, José María; López Alonso, José Manuel; Alda Serrano, JavierThe manufacture of a photonic crystal always produce deviations from the ideal case. In this paper we present a detailed analysis of the influence of the manufacture errors in the resulting electric field distribution of a photonic crystal microcavity. The electromagnetic field has been obtained from a FDTD algorithm. The results are studied by using the Principal Component Analysis method. This approach quantifies the influence of the error in the preservation of the spatial-temporal structure of electromagnetic modes of the ideal microcavity. The results show that the spatial structure of the excited mode is well preserved within the range of imperfection analyzed in the paper. The deviation from the ideal case has been described and quantitatively estimated.Item Design of Fresnel lenses and binary-staircase kinoforms of low value of the aperture number(Optics Communications, 2006) Alda Serrano, Javier; Rico García, José María; López Alonso, José Manuel; Lail, BrianThe design of plane Fresnel zone plates, and binary-staircase kinoforms, has been analyzed in this paper for a non-imaging application aimed to increase the performance of point-like detectors. They maximize the irradiance at the focal point of the diffractive element maintaining some constrains in the lateral size of the element. The design of the binary-staircase kinoform has been described as an iterative process. Some interesting results have been obtained for the values of the relative aperture number, or F/#. The practical case treated here produces elements with very low F/#. The results shows that the gain of the irradiance at the focal point increases with the focal distance of the binary-staircase kinoform, and decreases with the focal length for a plane Fresnel zone plate having a limited lateral size. The calculation of the width of the irradiance distribution makes it possible to select those solutions that best concentrate the irradiance on the focal plane. (c) 2005 Elsevier B.V. All rights reserved.