Scattering of surface plasmons by one-dimensional periodic nanoindented surfaces

In this work, the scattering of surface plasmons by a finite periodic array of one-dimensional grooves is theoretically analyzed by means of a modal expansion technique. We have found that the geometrical parameters of the array can be properly tuned to achieve optimal performance of the structure either as a Bragg reflector or as a converter of surface plasmons into light. In this last case, the emitted light is collimated within a few degrees cone. Importantly, we also show that a small number of indentations in the array are sufficient to fully achieve its functional capabilities.Comment: 5 pages, 5 figures; changed sign convention in some definition

Contribución al atlas palinológico de Andalucía Occidental, VI. Caprifoliaceae

En el presente trabajo se l leva a cabo un estudio morfológico de los granos de pol en de Lonicera etrusca G. Santi , L. i mplexa Ai ton , L. pericl ymenum L. , L. splendida Boiss ., Sambucus ebulus L. , S.. nigra L. y Viburnum tinus L., tanto en microscopía óptica como electr ónica de barrido . Se reconocen tres t ipos de polen diferentes , para cuya separación han servido fundamenta lmente las aperturas y la ornamentación.The polleo morphology of Lonicera etrusca G. San t i, L. implexa Ai to'n , L. periclymenum L. , L. splendida Boiss . , Sacumbus ebul us L. , S. nigra L. and Viburnum tinus L. have benn s t udied by light and scanning electron mi croscopy . Three types of pollen are recognized using the apertures a nd the ornamenta ti e

Adaptive control of a solar furnace for material testing

IFAC Adaptive Systems in Control and Signal Processing. Glasgow. Scotland. UK. 26/08/1998This paper presents an adaptive control system for controlling the temperature of a solar furnace, which is a high solar concentrating facility made up of heliostats tracking the sun and reflecting solar radiation onto a static parabolic concentrating system at the focal spot of which a high percentage of the solar energy collected by the collector system is concentrated in a small area. A large attenuator (shutter) placed between the collector system and the concentrator serves to control the amount of solar energy used for heating the samples placed at the focal spot. The paper shows the results obtained in the application of adaptive PI controllers to a solar furnace, incorporating feedforward action, anti-windup and slew rate constraint handling mechanisms

Morfología polínica de la subfamilia rutoideae (Rutaceae) en Andalucía

Se estudia la morfol ogía pol ínica de Ruta montana , R. cha l e pens i s , R. angusti foli a , Haplophyllum linifolium , Dictamnus a lbus y D. hispanic us tanto al microscopio óptico como al el ectrónico de barrido . Se descr iben cuatro tipos polínicos diferentes en base al tamaño , grosor de la exina y ornamentaciónThe pollen of Ruta montana , R. chal epensis, R. angus t i f o l ia, Ha plophyllum l i ni folium, Dictamnus albus and D. hispani c us are studied by light and scanning electron microscope. Using the size , ex i ne' s thickness and ornamentation, fdur types of pol l en grains are recogni ze

Morfología polínica de la familia Primulaceae en Andalucía Occidental

Se estudia la morfología pol inica de nueve especi es de Pri mulaceae en Andalucia Occidental, pertenecientes a los géneros Prímula, Lysimac hia, Asterolinon, Anagallis y Samolus , tanto al microscopi o óptico como electrónico de barrido. Los resultados expuestos ponen de manifiesto e l c aracter euripolínico de esta fami l ia , observandose di f erencias en e l tamaño , número de aperturas y ornamentac iónThe polleo morphology of nine species of Primulaceae from W. Andaluc ía bel onging to the genera Primula, Lysimachia, Asterolinon, Anagallis and Samolus are studied by l ight and scanning electron microscopy . This fami ly is eurypalynous. Sorne diff erences in size, aperture number and ornamentation have been observed

Terahertz surface plasmon polariton propagation and focusing on periodically corrugated metal wires

In this letter we show how the dispersion relation of surface plasmon polaritons (SPPs) propagating along a perfectly conducting wire can be tailored by corrugating its surface with a periodic array of radial grooves. In this way, highly localized SPPs can be sustained in the terahertz region of the electromagnetic spectrum. Importantly, the propagation characteristics of these spoof SPPs can be controlled by the surface geometry, opening the way to important applications such as energy concentration on cylindrical wires and superfocusing using conical structures.Comment: accepted at PRL, submitted 29th May 200

Optical bistability in subwavelength apertures containing nonlinear media

We develop a self-consistent method to study the optical response of metallic gratings with nonlinear media embedded within their subwavelength slits. An optical Kerr nonlinearity is considered. Due to the large E-fields associated with the excitation of the transmission resonances appearing in this type of structures, moderate incoming fluxes result in drastic changes in the transmission spectra. Importantly, optical bistability is obtained for certain ranges of both flux and wavelength.Comment: 4 pages, 4 figure

Algunos recursos en internet para mejorar la enseñanza de la geografía

El gran aumento de información digitalizada, accesible on line, en un mundo globalizado, ha puesto a disposición del profesorado de Geografía y, en general, de Ciencias Sociales una gran cantidad de recursos que pueden ser utilizados en la enseñanza y también en la formación de los docentes. Algunos de estos recursos ya tenían cierta tradición de uso en formato convencional, apareciendo ahora más fácilmente accesibles; otros son nuevos recursos producidos digitalmente. Por ello tiene interés facilitar al profesorado una selección de estos recursos útiles para la enseñanza de la Geografía, organizados en diez grandes secciones temáticas, para un mejor aprovechamiento de los mismosThe great increase in on-line digital information in a global world has made available a great amount of resources that can be used by Geography and, in general, Social Sciences teachers in education and also in teacher training. Some of these resources already had a certain tradition of use in a conventional format but had now become more easily accessible; others are new digitally produced resources. That is why it is interesting to provide teachers a selection of these useful resources for Geography teaching, organized in ten great thematic sections in order to make a better use of them

On the transmission of light through a single rectangular hole

In this Letter we show that a single rectangular hole exhibits transmission resonances that appear near the cutoff wavelength of the hole waveguide. For light polarized with the electric field pointing along the short axis, it is shown that the normalized-to-area transmittance at resonance is proportional to the ratio between the long and short sides, and to the dielectric constant inside the hole. Importantly, this resonant transmission process is accompanied by a huge enhancement of the electric field at both entrance and exit interfaces of the hole. These findings open the possibility of using rectangular holes for spectroscopic purposes or for exploring non-linear effects.Comment: Submitted to PRL on Feb. 9th, 200

Transmission properties of a single metallic slit: From the subwavelength regime to the geometrical-optics limit

In this work we explore the transmission properties of a single slit in a metallic screen. We analyze the dependence of these properties on both slit width and angle of incident radiation. We study in detail the crossover between the subwavelength regime and the geometrical-optics limit. In the subwavelength regime, resonant transmission linked to the excitation of waveguide resonances is analyzed. Linewidth of these resonances and their associated electric field intensities are controlled by just the width of the slit. More complex transmission spectra appear when the wavelength of light is comparable to the slit width. Rapid oscillations associated to the emergence of different propagating modes inside the slit are the main features appearing in this regime.Comment: Accepted for publication in Phys. Rev.