Thermal switching of the scattering coefficients of terahertz surface plasmon polaritons impinging on a finite array of subwavelength grooves on semiconductor surfaces

8 págs.; 8 figs.; 1 tab. ; PACS number s : 73.20.Mf, 78.68. m, 65.40. b, 41.20.JbWe present a theoretical framework that allows us to investigate the scattering of terahertz surface plasmon polaritons (SPP's) by arrays of subwavelength grooves and ridges on semiconductors. The formulation is based on the reduced Rayleigh equation resulting upon imposing an impedance boundary condition. Guided by approximate estimations of the broadening with temperature of the first gap in the SPP dispersion relation in the case of indium antimonide samples with rectangular grooves, numerical calculations are carried out to determine the spectral dependence of all the SPP scattering channels (reflection, transmission, and radiation) in the immediate vicinity of that gap. The thermally induced switching of the SPP reflection and transmission nearby the lower SPP band edge is investigated as a function of groove parameters (size and number); near-field intensity maps are also presented. We thus shed light on the SPP scattering and switching physical mechanisms, thereby providing the most suitable experimental configurations. © 2006 The American Physical Society.This work was supported in part by the Spanish “Ministerio de Educación y Ciencia” Grant Nos. BFM2003-0427 and FIS2004-0108 and “Comunidad de Madrid” Grant MICROSERES and by the European Union Grant HPRN-CT- 2002-00206. The work of J.G.R. was supported by the “Stichting voor Fundamenteel Onderzoek der Materie” FOM, which is financially supported by the “Nederlandse Organisatie voor Wetenschappelijk Onderzoek” NWO.Peer Reviewe

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We demonstrate that the emission of light by fluorescent molecules in the proximity of periodic arrays of nanoantennas or plasmonic crystals can be strongly modified when the arrays are covered by a dielectric film. The coupling between localized surface plasmon resonances and photonic states leads to surface modes which increase the density of optical states and improve light extraction. Excited dye molecules preferentially decay radiatively into these modes, exhibiting an enhanced and directional emission.Comment: 5 figure

Tailor-made directional emission in nanoimprinted plasmonic-based light-emitting devices

We demonstrate an enhanced and tailor-made directional emission of light-emitting devices using nanoimprinted hexagonal arrays of aluminum nanoparticles. Fourier microscopy reveals that the luminescence of the device is not only determined by the material properties of the organic dye molecules but is also strongly influenced by the coherent scattering resulting from periodically arranged metal nanoparticles. Emitters can couple to lattice-induced hybrid plasmonic–photonic modes sustained by plasmonic arrays. Such modes enhance the spatial coherence of an emitting layer, allowing the efficient beaming of the emission along narrow angular and spectral ranges. We show that tailoring the separation of the nanoparticles in the array yields an accurate angular distribution of the emission. This combination of large-area metal nanostructures fabricated by nanoimprint lithography and light-emitting devices is beneficial for the design and optimization of solid-state lighting systems

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Strong modification of the reflection from birefringent layers of semiconductor nanowires by nanoshells

The propagation of light in layers of vertically aligned nanowires is determined by their unique and extreme optical properties. Depending on the nanowire filling fraction and their diameter, layers of nanowires form strongly birefringent media. This large birefringence gives rise to sharp angle dependent peaks in polarized reflection. We demonstrate experimentally the tunability of the reflection by adding shells of SiO2 with thicknesses ranging from 10¿nm to 30¿nm around the nanowires. The strong modification of the reflection peaks renders nanowire layers as a promising candidate for sensing applications

Effective fuel temperature of wwer-1000

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Una herramienta web para el cálculo y simulación de estructuras caché

Versión electrónica de la ponencia presentada en V Congreso de Tecnologías Aplicadas a la Enseñanza de la Electrónica, celebrado en Las Palmas de Gran Canaria en 2002La herramienta presentada facilita la resolución de problemas sencillos relacionados con el tamaño en bits de los campos en la palabra de direccionamiento, así como con el tamaño de la propia estructura de la unidad de memoria cache. Además permite la simulación del modo de operación de una memoria cache con unas características previamente seleccionadas. El objetivo es ayudar al alumno en la compresión del funcionamiento de la memoria cache y disponer de una herramienta que facilita el calculo de los parámetros asociados a su estructura. La aplicación se ha desarrollado en Java para que sea accesible desde la página web de la asignatura Arquitectura e Ingeniería de Computadores impartida en la E.T.S de Informática de la UAM

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Euan Hendry, Matthew J. Lockyear, J. Gómez Rivas, L. Kuipers, and M. Bonn, Physical Review B, Vol. 75, article 235305 (2007). "Copyright © 2007 by the American Physical Society."We demonstrate ultrafast optical switching of the transmission of terahertz radiation through a metal grating with subwavelength holes. By fabricating the grating on a semiconductor silicon substrate, we are able to control the grating transmission intensity by varying the photodoping level of the silicon and thereby the resonant coupling to the metal grating. As such, we are able to switch the transmission on picosecond time scales with low visible light intensities, observing a factor of 2–5 improvement in photomodulation efficiency at resonance wavelengths over a bare silicon surface

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