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Search Results: 1 - 10 of 197297 matches for " Jaime Gómez Rivas "
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Polarization-dependent light extinction in ensembles of polydisperse, vertical semiconductor nanowires: A Mie scattering effective medium
Grzegorz Grzela,Djamila Hourlier,Jaime Gómez Rivas
Physics , 2013, DOI: 10.1103/PhysRevB.86.045305
Abstract: We present an experimental and theoretical study of the angle- and polarization-dependent light extinction in random arrays of polydisperse semiconductor nanowires epitaxially grown on substrates. The specular reflectance is described by averaging the scattering properties of individual nanowires obtained from Lorenz-Mie theory over the diameter distribution. The complex effective refractive index describing the propagation and attenuation of the coherent beam scattered in forward direction is determined in the independent scattering approximation and used to calculate the angle- and polarization-dependent reflectance. Our measurements demonstrate the highly anisotropic scattering in ensembles of aligned nanowires.
Selective detection of bacterial layers with terahertz plasmonic antennas
Audrey Berrier,Martijn C. Schaafsma,Guillaume Nonglaton,Jonas Bergquist,Jaime Gómez Rivas
Physics , 2012, DOI: 10.1364/BOE.3.002937
Abstract: Current detection and identification of micro-organisms is based on either rather unspecific rapid microscopy or on more accurate complex, time-consuming procedures. In a medical context, the determination of the bacteria Gram type is of significant interest. The diagnostic of microbial infection often requires the identification of the microbiological agent responsible for the infection, or at least the identification of its family (Gram type), in a matter of minutes. In this work, we propose to use terahertz frequency range antennas for the enhanced selective detection of bacteria types. Several microorganisms are investigated by terahertz time-domain spectroscopy: a fast, contactless and damage-free investigation method to gain information on the presence and the nature of the microorganisms. We demonstrate that plasmonic antennas enhance the detection sensitivity for bacterial layers and allow the selective recognition of the Gram type of the bacteria.
Mapping the directional emission of quasi-two-dimensional photonic crystals of semiconductor nanowires using Fourier microscopy
Yannik Fontana,Grzegorz Grzela,Erik P. A. M. Bakkers,Jaime Gómez Rivas
Physics , 2013, DOI: 10.1103/PhysRevB.86.245303
Abstract: Controlling the dispersion and directionality of the emission of nanosources is one of the major goals of nanophotonics research. This control will allow the development of highly efficient nanosources even at the single photon level. One of the ways to achieve this goal is to couple the emission to Bloch modes of periodic structures. Here, we present the first measurements of the directional emission from nanowire photonic crystals by using Fourier microscopy. With this technique we efficiently collect and resolve the directional emission of nanowires within the numerical aperture of a microscope objective. The light emission from a heterostructure grown in each nanowire is governed by the photonic (Bloch) modes of the photonic crystal. We also demonstrate that the directionality of the emission can be easily controlled by infiltrating the photonic crystal with a high refractive index liquid. This work opens new possibilities for the control of the emission of sources in nanowires.
Broadband and omnidirectional anti-reflection layer for III/V multi-junction solar cells
Silke L. Diedenhofen,Grzegorz Grzela,Erik Haverkamp,Gerard Bauhuis,John Schermer,Jaime Gómez Rivas
Physics , 2012, DOI: 10.1016/j.solmat.2012.02.022
Abstract: We report a novel graded refractive index antireflection coating for III/V quadruple solar cells based on bottom-up grown tapered GaP nanowires. We have calculated the photocurrent density of an InGaP-GaAs-InGaAsP-InGaAs solar cell with a MgF2/ZnS double layer antireflection coating and with a graded refractive index coating. The photocurrent density can be increased by 5.9 % when the solar cell is coated with a graded refractive index layer with a thickness of 1\mu m. We propose to realize such a graded refractive index layer by growing tapered GaP nanowires on III/V solar cells. For a first demonstration of the feasibility of the growth of tapered nanowires on III/V solar cells, we have grown tapered GaP nanowires on AlInP/GaAs substrates. We show experimentally that the reflection from the nanowire coated substrate is reduced and that the transmission into the substrate is increased for a broad spectral and angular range.
Photo-generated THz antennas: All-optical control of plasmonic materials
Giorgos Georgiou,Hemant K. Tyagi,Peter Mulder,Gerard J. Bauhuis,John J. Schermer,Jaime Gómez Rivas
Physics , 2013,
Abstract: Localized surface plasmon polaritons in conducting structures give rise to enhancements of electromagnetic local fields and extinction efficiencies. Resonant conducting structures are conventionally fabricated with a fixed geometry that determines their plasmonic response. Here, we challenge this conventional approach by demonstrating the photo-generation of plasmonic materials (THz plasmonic antennas) on a flat semiconductor layer by the structured optical illumination through a spatial light modulator. Free charge carriers are photo-excited only on selected areas, which enables the definition of different plasmonic antennas on the same sample by simply changing the illumination pattern, thus without the need of physically structuring the sample. These results open a wide range of possibilities for an all-optical spatial and temporal control of resonances on plasmonic surfaces and the concomitant control of THz extinction and local field enhancements.
Excitation of confined modes on particle arrays
Xesús Manoel Benda?a,Gabriel Lozano,Giuseppe Pirruccio,Jaime Gómez Rivas,F. Javier García de Abajo
Physics , 2012,
Abstract: We describe both theoretically and experimentally the existence and excitation of confined modes in planar arrays of gold nanodisks. Ordered 2D lattices of monodispersive nanoparticles are manufactured, embedded in a silica matrix, and exposed to evanescent prism-coupling illumination, leading to dark features in the reflectivity, which signal the presence of confined modes guided along the arrays. We find remarkable agreement between theory and experiment in the frequency-momentum dispersion of the resonances. Direct excitation of these modes reveals long propagation distances and deep extinction features. This characterization of guided modes shows the great potential of metallic particle arrays for optical signal processing and distant sensing applications.
Detection of deep-subwavelength dielectric layers at terahertz frequencies using semiconductor plasmonic resonators
Audrey Berrier,Pablo Albella,M. Ameen Poyli,Ronald Ulbricht,Mischa Bonn,Javier Aizpurua,Jaime Gómez Rivas
Physics , 2012, DOI: 10.1364/OE.20.005052
Abstract: Plasmonic bowtie antennas made of doped silicon can operate as plasmonic resonators at terahertz (THz) frequencies and provide large field enhancement close to their gap. We demonstrate both experimentally and theoretically that the field confinement close to the surface of the antenna enables the detection of ultrathin (100 nm) inorganic films, about 3750 times thinner than the free space wavelength. Based on model calculations, we conclude that the detection sensitivity and its variation with the thickness of the deposited layer are related to both the decay of the local THz field profile around the antenna and the local field enhancement in the gap of the bowtie antenna. This large field enhancement has the potential to improve the detection limits of plasmon-based biological and chemical sensors.
Los tratados De Iure Belli y el origen del Derecho Internacional. Una aproximación historiográfica a los estudios sobre el derecho de la guerra durante el primer franquismo
Gómez Rivas, León
Hispania Sacra : Revista de Historia Eclesiástica , 2010,
Abstract: The name School of Salamanca is refered to a group of theologians and Natural Law philosophers who taught in the University of Salamanca, following the inspiration of the great tomist Francisco de Vitoria. They developed some original theories about Economy or International Law, in such a modern point of view, beginning from some very interesting Treatises on Justice or the Law of War and Peace, as we will see next. Es bien conocida la aportación de la Escuela de Salamanca (siglos XVI y XVII) en el campo de la economía, la política o el derecho. En esta última disciplina, ya a comienzos del siglo XX se puso de manifiesto el influjo de Francisco de Vitoria y sus discípulos en los orígenes del moderno Derecho Internacional, precisamente a raíz de un buen número de tratados sobre el tema que presentamos a continuación: el derecho de la guerra, ofreciendo un balance historiográfico sobre aquellos autores escolásticos y su influencia durante el llamado primer franquismo.
Jaime Saravia Gómez
Infectio , 2006,
The Multiorgamic Dysfunction Syndrome in pediatric population
Jaime Forero Gómez
MedUNAB , 2004,
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