Second harmonic generation from metallic arrays of rectangular holes

The generation process of second harmonic (SH) radiation from holes periodically arranged on a metal surface is investigated. Three main modulating factors affecting the optical response are identified: the near-field distribution at the wavelength of the fundamental harmonic, how SH light couples to the diffraction orders of the lattice, and its propagation properties inside the holes. It is shown that light generated at the second harmonic can excite electromagnetic modes otherwise inaccessible in the linear regime under normal incidence illumination. It is demonstrated that the emission of SH radiation is only allowed along off-normal paths precisely due to that symmetry. Two different regimes are studied in the context of extraordinary optical transmission, where enhanced linear transmission either occurs through localized electromagnetic modes or is aided by surface plasmon polaritons (SPPs). While localized resonances in metallic hole arrays have been previously investigated, the role played by SPPs in SH generation has not been addressed so far. In general, good agreement is found between our calculations (based on the finite difference time domain method) and the experimental results on localized resonances, even though no free fitting parameters were used in describing the materials. It is found that SH emission is strongly modulated by enhanced fields at the fundamental wavelength (either localized or surface plasmon modes) on the glass metal interface. This is so in the transmission side but also in reflection, where emission can only be explained by an efficient tunneling of SH photons through the holes from the output to the input side. Finally, the existence of a dark SPP at the fundamental field is identified through a noninvasive method for the first time, by analyzing the efficiency and far-field pattern distribution in transmission at the second harmonic.Comment: This paper was published in JOSA B and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/josab/abstract.cfm?URI=josab-32-1-15. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under la

Business process reengineering role in electronic government

Business Process Reengineering (BPR) came up as a key concept in the 1990s, with a high impact on management and transactions of private companies. However, it has not been so well accepted in public administration. Nowadays, many projects for changes in government are related to electronic government. According to this, this article discusses the role of BPR in this context, its contribution to this kind of initiative, and if it is a required element to go forward. Also, the difficulties in carrying out the BPR in the particular case of e-government are analyzed, taking into account the characteristics of this kind of project, the stages that are generally involved and the environment in which it is performed. Finally, a basic structure for the development of egovernment is provided, specifying the insertion of BPR for reaching a more efficient, effective and foreseeable management of new projects.The past and the future of information systems: 1976-2006 and beyondRed de Universidades con Carreras en Informática (RedUNCI

Experimental hybridization and reproductive isolation between two sympatric species of tephritid fruit flies in the Anastrepha fraterculus species group

Among tephritid fruit flies, hybridzation has been found to produce local adaptationand speciation, and in the case of pest species, induce behavioral and ecological alterations that can adversely impact efficient pest management. The fraterculus species group within Anastrepha (Diptera: Tephritidae), is a rapidly radiating aggregate, which includes cryptic species complexes, numerous sister species, and several pest species. Molecular studies have highlighted the possibility of introgression between A. fraterculus and A. obliqua. Reproductive isolation has been studied among morphotypes of the A. fraterculus species complex as a tool for species delimitation. Here we examined the existence and strength ofprezygotic and postzygotic isolation between sympatric populations of two closely related species within the highly derived fraterculus group (A. fraterculus and A. obliqua), coexisting in nature. Although adults of both species showed a strong tendency for assortative mating, a small proportion of hybrid pairings in both directions were observed. We also observed asymetric postzygotic isolation, with one hybrid cross displaying a strong reduction in fecundity and F1 egg fertility. Survival was greater for the progeny of homotypic and hybrid crosses in the maternal host. There was a marked female biased sex ratio distortion for both F1 hybrid adults. Hybridization between A. fraterculus and A. obliqua in nature may be difficult but possible; these two species display stronger reproductive isolation than all pairsof species previously examined in the A. fraterculus species complex. Asymetric postzygotic isolation is suggestive of Wolbachia mediated cytoplasmic incompatibilities that may be exploited in area-wide pest management.Fil: Rull Gabayet, Juan Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Planta Piloto de Procesos Industriales Microbiologicos; ArgentinaFil: Tadeo, Eduardo. Instituto de Ecología A. C. . Red de Manejo Biorracional de Plagas y Vectores; MéxicoFil: Lasa, Rodrigo. Instituto de Ecología A. C. . Red de Manejo Biorracional de Plagas y Vectores; MéxicoFil: Rodríguez, Christian L.. Instituto de Ecología A. C. . Red de Manejo Biorracional de Plagas y Vectores; MéxicoFil: Altuzar Molina, Alma. Instituto de Ecología A. C. . Red de Manejo Biorracional de Plagas y Vectores; MéxicoFil: Aluja, Martín. Instituto de Ecología A. C. . Red de Manejo Biorracional de Plagas y Vectores; Méxic

Influence of material properties on extraordinary optical transmission through hole arrays

We present a theoretical study, based on the finite difference time domain method, of the optical response of circular hole arrays drilled in several metal films (Ag, Au, Cu, Al, Ni, Cr, and W). Two series of structures are studied. In the first one, transmittance peaks are analyzed as all geometrical parameters defining the system are scaled, except for the metal thickness which is kept constant, showing good agreement with existing experimental data. In the second series, the metal thickness is also scaled. This allows a clear distinction in the behavior of different metals: Ag, Au, and Cu show even larger transmittance peaks than hole arrays in a perfect conductor with the same nominal parameters. This is due to both a larger effective hole area and smaller absorption. In the case of Ni and Cr, the transmittance is much smaller due to absorption. Band structure calculations confirm that surface electromagnetic modes sustained by the perforated metal film are responsible for the extraordinary optical transmission phenomenon

Theory of light transmission through an array of rectangular holes

In a two-dimensional array of rectangular holes perforated on a metallic film, two mechanisms leading to enhanced transmission of light operate: excitation of surface plasmon polaritons (SPPs) and localized resonances that are also present in single holes. In this paper, we analyze theoretically how the two mechanisms evolve and mix when the period of the array is varied. We also demonstrate that absorption in the metal is the main limiting factor for the SPP-based enhanced transmission

Holey metal films: From extraordinary transmission to negative-index behavior

In this paper we study the common physical background of the phenomenon of extraordinary optical transmission in holey metal films and the emergence of the negative refractive index behavior in double fishnet structures. Here we provide further evidence that the resonant magnetic response of the latter structures is associated with the excitation of gap surface plasmon modes. The evolution of the optical response with the number of double fishnet layers is also addressed, finding that the effective refractive index reaches a converged value for a moderate number of layers

Business process reengineering role in electronic government

Business Process Reengineering (BPR) came up as a key concept in the 1990s, with a high impact on management and transactions of private companies. However, it has not been so well accepted in public administration. Nowadays, many projects for changes in government are related to electronic government. According to this, this article discusses the role of BPR in this context, its contribution to this kind of initiative, and if it is a required element to go forward. Also, the difficulties in carrying out the BPR in the particular case of e-government are analyzed, taking into account the characteristics of this kind of project, the stages that are generally involved and the environment in which it is performed. Finally, a basic structure for the development of egovernment is provided, specifying the insertion of BPR for reaching a more efficient, effective and foreseeable management of new projects.The past and the future of information systems: 1976-2006 and beyondRed de Universidades con Carreras en Informática (RedUNCI

Guiding and Focusing of Electromagnetic Fields with Wedge Plasmon Polaritons

We study theoretically electromagnetic modes guided by metallic wedges at telecom wavelengths. These modes are found to exhibit superior confinement while showing similar propagation loss as compared to other subwavelength guiding configurations. It is also shown that mode focusing can be realized by gradual modification of the wedge geometry along the mode propagation direction

In the diffraction shadow: Norton waves versus surface plasmon-polaritons in the optical region

Surface electromagnetic modes supported by metal surfaces have a great potential for uses in miniaturised detectors and optical circuits. For many applications these modes are excited locally. In the optical regime, Surface Plasmon Polaritons (SPPs) have been thought to dominate the fields at the surface, beyond a transition region comprising 3-4 wavelengths from the source. In this work we demonstrate that at sufficiently long distances SPPs are not the main contribution to the field. Instead, for all metals, a different type of wave prevails, which we term Norton waves for their reminiscence to those found in the radio-wave regime at the surface of the Earth. Our results show that Norton Waves are stronger at the surface than SPPs at distances larger than 6-9 SPP's absorption lengths, the precise value depending on wavelength and metal. Moreover, Norton waves decay more slowly than SPPs in the direction normal to the surface.Comment: 8 pages, 8 figure