Person: Alda Serrano, Javier
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First Name
Javier
Last Name
Alda Serrano
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Óptica y Optometría
Department
Óptica
Area
Optica
Identifiers
7 results
Search Results
Now showing 1 - 7 of 7
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 Application of tomographic techniques to the spatial-response mapping of antenna-coupled detectors in the visible(Applied Optics, 2008) Rico García, José María; Sánchez Brea, Luis Miguel; Alda Serrano, JavierA tomographiclike method based on the inverse radon transform is used to retrieve the irradiance map of a focused laser beam. The results obtained from multiple knife-edge measurements have been processed through a kriging technique. This technique allows us to map both the beam irradiance and the uncertainty associated with the measurement method. The results are compared with those achieved in the standard fitting of two orthogonal knife-edge profiles to a modeled beam. The application of the tomographiclike technique does not require any beam model and produces a higher signal-to-noise ratio than the conventional method. As a consequence, the quality of the estimation of the spatial response map of an antenna-coupled detector in the visible is improved.Item Characterization of FDTD artifacts and modes in photonic crystals(Proceedings of SPIE, 2004) López Alonso, José Manuel; Rico García, José María; Alda Serrano, JavierFDTD algorithms are being used as a numeric tool for the analysis of photonic crystals. The definition of the modes associated with them is of interest for the study of the capabilities of photonic crystal devices. The Principal Component Analysis (PCA) has been applied here to a sequence of images corresponding to the electromagnetic fields obtained from the FDTD simulations. PCA has revealed and quantified the importance of the modes appearing in the photonic crystals. The capability of PCA to produce spatial structures, or maps, associated with temporal evolutions has made possible the calculation of the modulus and phase of the modes existing in the photonic crystal. Some other modes, contributing with an almost negligible amount to the total variance of the original data, are also revealed by the method. Besides, PCA has been used to quantify the contribution of the numerical noise of the algorithm and to identify the effect of artifacts related with the matching of the computational grid and the inner geometry of the photonic crystal.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 Finite-difference time-domain simulation of low-F# Fresnel zone plates coupled to IR antennas(Proceedings of SPIE, 2004) Rico García, José María; López Alonso, José Manuel; Lail, Brian; Boreman, Glenn; Alda Serrano, JavierFresnel Zone Plate Lenses (FZPLs) have been successfully coupled to infrared (IR) antennas producing a responsivity enhancement of about two orders of magnitude. However, their lateral extension may compromise their applicability in focal-plane-arrays (FPA) IR imagers, where the dimensions of the pixel are constrained by the FPA spacing. When designing optimum-gain FZPLs for FPAs, we are lead to the requirement of FZPLs operating at very low F/#s (marginal rays propagating at a large angle in image space). In this case, Finite-Difference Time-Domain techniques (FDTD) are used to refine the physical-optics modelling results, producing a result closer to the actual case encountered in a high-fill-factor FPA. In this contribution, we analyze the FZPL designs by using FDTD techniques. The main result of the FDTD computation is the gain factor defined as the ratio of the response of the IR antennas coupled with the FZPL, compared to the same antennas without the FZPL.Item Spectral and thermal management of hexagonal resonant structures for flexible opto-electronic transducers(Optics and Laser Technology, 2024) Hamdy Mohamed Elshorbagy, Mahmoud; Torres Lechuga, Luis G.; González, Francisco J.; Alda Serrano, Javier; Cuadrado Conde, AlexanderEfficient on-chip optoelectronic devices in sensing and energy harvesting rely on the combination of subwavelength designs and multiphysical effects. In this contribution, we experimentally analyze and computationally model the optical performance of a hexagonal two-dimensional cluster placed over a silicon substrate and separated by a dielectric layer. Its reflectance has a dip in the long wavelength infrared band. This resonance is due to the generation of localized surface plasmons at the hexagonal surface. Our experimental results validate the multiphysics computational model which can be used to improve its performance as thermal detectors on flexible substrates. In this case, the model combines computational electromagnetism and heat transfer analysis to obtain the temperature distribution in the device. From this analysis, we have designed a thermal transducer based on a metasurface. It consists of a stacked arrangement made of a periodic hexagonal metallic array, a semiconductor ultra-thin layer, a metallic mirror, and a flexible substrate made of polyimide. The structure presented in this work behaves as a spectral selective surface with a resonant wavelength determined by the size of the hexagonal elements and the configuration of the multilayer. Our results show that this device has a time constant in the order of a few milliseconds (2.3 ms). This fast response can be useful in a wide variety of applications such as high speed thermal sensing and energy harvesting.Item Optical Sensing Using Hybrid Multilayer Grating Metasurfaces with Customized Spectral Response(Sensors, 2024) Hamdy Mohamed Elshorbagy, Mahmoud; Cuadrado Conde, Alexander; Alda Serrano, JavierCustomized metasurfaces allow for controlling optical responses in photonic and optoelectronic devices over a broad band. For sensing applications, the spectral response of an optical device can be narrowed to a few nanometers, which enhances its capabilities to detect environmental changes that shift the spectral transmission or reflection. These nanophotonic elements are key for the new generation of plasmonic optical sensors with custom responses and custom modes of operation. In our design, the metallic top electrode of a hydrogenated amorphous silicon thin-film solar cell is combined with a metasurface fabricated as a hybrid dielectric multilayer grating. This arrangement generates a plasmonic resonance on top of the active layer of the cell, which enhances the optoelectronic response of the system over a very narrow spectral band. Then, the solar cell becomes a sensor with a response that is highly dependent on the optical properties of the medium on top of it. The maximum sensitivity and figure of merit (FOM) are SB = 36,707 (mA/W)/RIU and ≈167 RIU−1, respectively, for the 560 nm wavelength using TE polarization. The optical response and the high sensing performance of this device make it suitable for detecting very tiny changes in gas media. This is of great importance for monitoring air quality and thecomposition of gases in closed atmospheres.