Igor Campillo - Academia.edu (original) (raw)

Papers by Igor Campillo

Trabajo presentado al XXIV Simposium Nacional de la Union Cientifica Internacional de Radio. Sant... more Trabajo presentado al XXIV Simposium Nacional de la Union Cientifica Internacional de Radio. Santander, 2009

Resumen Fecha de solicitud: 26/02/2004.--Titulares: Fundación Labein, Consejo Superior de Investi... more Resumen Fecha de solicitud: 26/02/2004.--Titulares: Fundación Labein, Consejo Superior de Investigaciones Científicas (CSIC).| This invention relates to building cement comprising, as a first component, belite clinker, and which is suitable for, among others, mortars and ...

Phys Rev B, 2011

In this paper we report directivity enhancement by a short-focal-length plano-concave lens engine... more In this paper we report directivity enhancement by a short-focal-length plano-concave lens engineered by stacked subwavelength hole arrays (fishnet-like stack) with an effective negative index of refraction close to zero, n → 0, that arises from ɛ and μ near-zero extreme values. The plano-concave lens frequency response shows two enhancement peaks, one at the wavelength corresponding to n = -1 and, prominent in this configuration, another unexpected peak when n → 0 that comes as a result of the similar low values of ɛ and μ. The frequency-dependent negative refractive index and beam-forming properties of the lens are supported by finite-integration-frequency- and time-domain simulations and experimental results. This near-zero metamaterial lens can find applications in terahertz and even optics since the building block, stacked extraordinary optical transmission layers, has already been reported for those regimes under the name of fishnet structure.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1998

The electronic stopping power suered by ions penetrating periodic crystals is investigated within... more The electronic stopping power suered by ions penetrating periodic crystals is investigated within linear response theory. A full treatment of the dynamical response of valence electrons is made, starting from a realistic description of the one-electron band structure and using ab initio non-local pseudopotentials. The dynamical density-response function is obtained in the random-phase approximation. Results for the stopping power of aluminum averaged over impact parameters are presented.

El estudio del comportamiento de las excitaciones individuales y colectivas de los constituyentes... more El estudio del comportamiento de las excitaciones individuales y colectivas de los constituyentes de la materia es uno de los grandes retos de la Fisica. El presente trabajo consta de dos partes diferenciadas. La primera parte se dedica al estudio de fenomenos no lineales en la interaccion de cargas con el gas de electrones homogeneo. Haciendo uso de tecnicas diagramaticas se ha investigado la excitacion de plasmones dobles que acompana al paso de electrones rapidos a traves de metales, se analizan las contribuciones de plasmones y excitaciones individuales electron-hueco en el termino Z3 del poder de frenado, y se evalua de forma rigurosa la distribucion espacial del potencial y la densidad inducidos cuadraticos. La segunda parte se centra en el estudio de la funcion de respuesta dinamica de solidos reales. Con el desarrollo de las tecnicas ab initio es posible abordar el estudio de la dinamica electronica desde un punto de vista mas realista, asumiendo el hecho de que el solido es un medio anisotropo, que los electrones se mueven en una red de iones, y teniendo en cuenta, en los metales de transicion, el papel de los electrones de tipo d de una manera consistente. Asi, se presenta inicialmente el formalismo basico de la funcion de respuesta lineal y de su construccion ab initio. Se reproducen los calculos realizados hasta la fecha de la funcion de respuesta de aluminio y silicio y se presenta, por primera vez, la evaluacion y discusion de la respuesta dinamica del cobre. Posteriormente, se aplican las tecnicas ab initio al estudio del poder de frenado de solidos reales y, en particular, de aluminio y de silicio. Finalmente, se investiga el tiempo de vida de electrones excitados cerca del nivel de Fermi en cobre y aluminio.

A survey is presented of the theoretical status of quadratic response theories for the understand... more A survey is presented of the theoretical status of quadratic response theories for the understanding of nonlinear aspects in the interaction of charged particles with matter. In the frame of the many-body perturbation theory we study the interaction of charged particles with the electron gas, within the random-phase approximation (RPA). In particular, nonlinear corrections to the stopping power of an electron gas for ions are analyzed, and special emphasis is made on the contribution to the stopping power coming from the excitation of single and double plasmons. Double plasmon mean free paths of swift electrons passing through an electron gas are also discussed.

Sponsors: European Space Agency; Conference code: 67919

Physical Review B, 2000

We present first-principles calculations of electron-electron scattering rates of low-energy elec... more We present first-principles calculations of electron-electron scattering rates of low-energy electrons in Au. Our full band-structure calculations indicate that a major contribution from occupied d states participating in the screening of electron-electron interactions yields lifetimes of electrons in Au with energies of 1.0-3.0 eV above the Fermi level that are larger than those of electrons in a free-electron gas by a factor of ϳ4.5. This prediction is in agreement with a recent experimental study of ultrafast electron dynamics in Au͑111͒ films ͓J. Cao et al., Phys. Rev. B 58, 10 948 ͑1998͔͒, where electron transport has been shown to play a minor role in the measured lifetimes of hot electrons in this material.

Physical Review B, 2000

First-principles calculations of the inelastic lifetime of low-energy electrons in Al, Mg, Be, an... more First-principles calculations of the inelastic lifetime of low-energy electrons in Al, Mg, Be, and Cu are reported. Quasiparticle damping rates are evaluated from the knowledge of the electron selfenergy, which we compute within the GW approximation of many-body theory. Inelastic lifetimes are then obtained along various directions of the electron wave vector, with full inclusion of the band structure of the solid. Average lifetimes are also reported, as a function of the electron energy. In Al and Mg, splitting of the band structure over the Fermi level yields electron lifetimes that are smaller than those of electrons in a free-electron gas. Larger lifetimes are found in Be, as a result of the characteristic dip that this material presents in the density of states near the Fermi level. In Cu, a major contribution from d electrons participating in the screening of electron-electron interactions yields electron lifetimes which are well above those of electrons in a free-electron gas with the electron density equal to that of valence (4s 1) electrons.

Physical Review B, 1999

The role of localized d-bands in the dynamical response of Cu is investigated, on the basis of ab... more The role of localized d-bands in the dynamical response of Cu is investigated, on the basis of ab initio pseudopotential calculations. The density-response function is evaluated in both the random-phase approximation (RPA) and a time-dependent local-density functional approximation (TDLDA). Our results indicate that in addition to providing a polarizable background which lowers the free-electron plasma frequency, d-electrons are responsible, at higher energies and small momenta, for a doublepeak structure in the dynamical structure factor. These results are in agreement with the experimentally determined optical response of copper. We also analyze the dependence of dynamical scattering cross sections on the momentum transfer.

MELECON 2006 - 2006 IEEE Mediterranean Electrotechnical Conference

ABSTRACT

2007 Joint 32nd International Conference on Infrared and Millimeter Waves and the 15th International Conference on Terahertz Electronics, 2007

Ventilator-associated pneumonia (VAP), viewed as an inevitable consequence of critical illness, i... more Ventilator-associated pneumonia (VAP), viewed as an inevitable consequence of critical illness, is increasingly accepted as an avoidable adverse health care incident. Whereas morbidity and mortality from VAP is well-documented in adults, it is poorly studied in children.This investigation was conducted to determine characteristics and possible risk factors for VAP, in critically ill neonates admitted to the neonatal intensive care unit (NICU). According to clinical pulmonary infection score (CPIS), 33 neonates were selected as having VAP and 24 neonates who did not develop VAP were assigned as non-VAP group. All neonates were subjected to case history, clinical examination, ABG, chest X-ray, and laboratory investigations (CBC, serum albumin, serum CRP, and blood culture). Neonates with VAP were subjected to broncheo-alveolar lavage (BAL) sampling. The BAL samples were subjected to macroscopic and microscopic examination, as well as quantitative cultures. Obtained results revealed that indications for mechanical ventilation (MV) included respiratory distress syndrome (RDS), congenital pneumonia, meconium aspiration syndrome (MAS), and hypoxic ischemic encephalopathy (HIE), with nonsignificant differences between VAP group and non-VAP group. VAP rates were significantly increased with decreased body weight and gestational age and with increased duration of NICU admission, duration of MV and use of invasive maneuvers. VAP was significantly associated with hypothermia, mucopurulent endotracheal tube (ETT) secretions, and radiological findings. The use of inotrops and corticosteroids was significantly noted among neonates with VAP than that among non-VAP neonates. Raised serum C-reactive protein (CRP), hypoalbuminemia and positive blood cultures were significantly associated with increased VAP rates. Cultures of BAL samples revealed Klebsiella pneumoniae (in 33%), Pseudomonas aeruginosa (in 21%), Staphylococcus aureus (in 15%), Escherichia coli (in 15%), Pneumococci (in 6%) and Candida albicans (in 9%). There was nonsignificant similarity in the type of organisms cultivated from either blood or BAL. In conclusion risk factors for the development of VAP include; 1) decreased body weight and gestational age, 2) increased duration of NICU admission, MV, and use of invasive maneuvers, 3) hypothermia, mucopurulent ETT secretions and the use of inotrops/ corticosteroids, 4) raised serum CRP, hypoalbuminemia and positive blood cultures and 5) nosocomial infection by Klebsiella, Pseudomonas, Staph aureus, E coli and Candida. [Mona Afify, Salha AI-Zahrani and Maha A Nouh. Risk Factors for the Development of Ventilator-Associated Pneumonia in Critically-Ill Neonates.

Nanotechnology in Construction 3, 2009

Calcium leaching is a degradation process consisting in the progressive dissolution of the cement... more Calcium leaching is a degradation process consisting in the progressive dissolution of the cement paste as a consequence of the migration of the calcium ions to the aggressive solution. Although the most important changes take place at the nano-and micro-scale, their consequences are observed at every length scale. Within this work, a multi-scale approach combining a wide variety of experimental techniques was used to study such phenomenon in cement pastes with silica nanoparticles. The experimental results proved that the pozzolanic reaction induced by the nanoparticles resulted in a C-S-H gel more stable chemically and with longer silicate chains. In addition, the reduction of the amount of portlandite gave place to pastes with improved microstructure. As a consequence, the performances of such pastes were greatly enhanced both before and during the degradation process.

IEEE Antennas and Propagation Society Symposium, 2004., 2004

We show that the phenomenon of extraordinary transmission though arrays of subwavelength holes is... more We show that the phenomenon of extraordinary transmission though arrays of subwavelength holes is also present in the microwave range as it occurs in the optical regime. Following simulations of the influence of the number of holes, a prototype has been designed and fabricated in an aluminum plate. By using a millimeter wave quasioptical vector network analyzer in the range between 40 GHz and 110 GHz, measurements of the transmission response have been performed. A resonant total transmission at wavelengths close to the period of the array appears in the spectra opening the possibility of exciting future applications.

2008 33rd International Conference on Infrared, Millimeter and Terahertz Waves, 2008

ABSTRACT Here, we present for the first time experimental results of the phenomenon of extraordin... more ABSTRACT Here, we present for the first time experimental results of the phenomenon of extraordinary transmission through double periodic arrays of subwavelength holes at 220 GHz. Prototypes have been designed and fabricated by deposition of a thin Aluminum layer over a polypropylene wafer. These simulation results show a resonant total transmission at wavelengths close to the long period of the array. The transmission response measurements will be performed with a Millimeter Wave Quasioptical Vector Network Analyzer in the range between 40 GHz and 260 GHz. These results can give rise to interesting applications in the emerging Metamaterials field.

2008 33rd International Conference on Infrared, Millimeter and Terahertz Waves, 2008

ABSTRACT In this work, by using an extraordinary transmission metamaterial prism and taking advan... more ABSTRACT In this work, by using an extraordinary transmission metamaterial prism and taking advance of its inherent dispersive behavior, the feasibility of manufacturing a multiplexer/demultiplexer at millimeter-wave is shown. Depending on the incoming beam frequency, the outgoing beam suffers a different deflection (governed by Snell's law). Since the frequency dependent index of refraction of this metamaterial can go from almost zero to -2 for the first propagation band, different negative outgoing angles can be obtained and then, diverse paths for each frequency, as the near-field experimental results confirm.

2009 IEEE International Workshop on Antenna Technology, 2009

Abstract A planoconcave parabolic lens exhibiting a negative index has been fabricated by using s... more Abstract A planoconcave parabolic lens exhibiting a negative index has been fabricated by using stacked subwavelength hole arrays as a route to build a metamaterial operating at millimeter wavelengths. The design consists of a staircase approximation of the ideal ...

Infrared and Millimeter Waves, Conference Digest of the 2004 Joint 29th International Conference on 2004 and 12th International Conference on Terahertz Electronics, 2004.

ABSTRACT This paper shows several possibilities for the design of metasurfaces based on etching h... more ABSTRACT This paper shows several possibilities for the design of metasurfaces based on etching holes in metallic plates, making corrugations surrounding an slit on the plate, and by introducing the concept of complementary split ring resonator. Enhanced transmission phenomena has been experimentally demonstrated in all three cases.

Physical Review B, 1998

Ab initio calculations of the electronic energy loss of ions moving in aluminum crystal are prese... more Ab initio calculations of the electronic energy loss of ions moving in aluminum crystal are presented, within linear-response theory, from a realistic description of the one-electron band-structure and a full treatment of the dynamical electronic response of valence electrons. For the evaluation of the density-response function we use the random-phase approximation and, also, a time-dependent extension of local-density functional theory. We evaluate both position-dependent and random stopping powers, for a wide range of projectile velocities. Our results indicate that at low velocities band structure effects slightly enhance the stopping power. At velocities just above the threshold velocity for plasmon excitation, the stopping power of the real solid is found to be smaller than that of jellium electrons, corrections being of about 10%. This reduction can be understood from sum rule arguments.

Trabajo presentado al XXIV Simposium Nacional de la Union Cientifica Internacional de Radio. Sant... more Trabajo presentado al XXIV Simposium Nacional de la Union Cientifica Internacional de Radio. Santander, 2009

Resumen Fecha de solicitud: 26/02/2004.--Titulares: Fundación Labein, Consejo Superior de Investi... more Resumen Fecha de solicitud: 26/02/2004.--Titulares: Fundación Labein, Consejo Superior de Investigaciones Científicas (CSIC).| This invention relates to building cement comprising, as a first component, belite clinker, and which is suitable for, among others, mortars and ...

Phys Rev B, 2011

In this paper we report directivity enhancement by a short-focal-length plano-concave lens engine... more In this paper we report directivity enhancement by a short-focal-length plano-concave lens engineered by stacked subwavelength hole arrays (fishnet-like stack) with an effective negative index of refraction close to zero, n → 0, that arises from ɛ and μ near-zero extreme values. The plano-concave lens frequency response shows two enhancement peaks, one at the wavelength corresponding to n = -1 and, prominent in this configuration, another unexpected peak when n → 0 that comes as a result of the similar low values of ɛ and μ. The frequency-dependent negative refractive index and beam-forming properties of the lens are supported by finite-integration-frequency- and time-domain simulations and experimental results. This near-zero metamaterial lens can find applications in terahertz and even optics since the building block, stacked extraordinary optical transmission layers, has already been reported for those regimes under the name of fishnet structure.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1998

The electronic stopping power suered by ions penetrating periodic crystals is investigated within... more The electronic stopping power suered by ions penetrating periodic crystals is investigated within linear response theory. A full treatment of the dynamical response of valence electrons is made, starting from a realistic description of the one-electron band structure and using ab initio non-local pseudopotentials. The dynamical density-response function is obtained in the random-phase approximation. Results for the stopping power of aluminum averaged over impact parameters are presented.

El estudio del comportamiento de las excitaciones individuales y colectivas de los constituyentes... more El estudio del comportamiento de las excitaciones individuales y colectivas de los constituyentes de la materia es uno de los grandes retos de la Fisica. El presente trabajo consta de dos partes diferenciadas. La primera parte se dedica al estudio de fenomenos no lineales en la interaccion de cargas con el gas de electrones homogeneo. Haciendo uso de tecnicas diagramaticas se ha investigado la excitacion de plasmones dobles que acompana al paso de electrones rapidos a traves de metales, se analizan las contribuciones de plasmones y excitaciones individuales electron-hueco en el termino Z3 del poder de frenado, y se evalua de forma rigurosa la distribucion espacial del potencial y la densidad inducidos cuadraticos. La segunda parte se centra en el estudio de la funcion de respuesta dinamica de solidos reales. Con el desarrollo de las tecnicas ab initio es posible abordar el estudio de la dinamica electronica desde un punto de vista mas realista, asumiendo el hecho de que el solido es un medio anisotropo, que los electrones se mueven en una red de iones, y teniendo en cuenta, en los metales de transicion, el papel de los electrones de tipo d de una manera consistente. Asi, se presenta inicialmente el formalismo basico de la funcion de respuesta lineal y de su construccion ab initio. Se reproducen los calculos realizados hasta la fecha de la funcion de respuesta de aluminio y silicio y se presenta, por primera vez, la evaluacion y discusion de la respuesta dinamica del cobre. Posteriormente, se aplican las tecnicas ab initio al estudio del poder de frenado de solidos reales y, en particular, de aluminio y de silicio. Finalmente, se investiga el tiempo de vida de electrones excitados cerca del nivel de Fermi en cobre y aluminio.

A survey is presented of the theoretical status of quadratic response theories for the understand... more A survey is presented of the theoretical status of quadratic response theories for the understanding of nonlinear aspects in the interaction of charged particles with matter. In the frame of the many-body perturbation theory we study the interaction of charged particles with the electron gas, within the random-phase approximation (RPA). In particular, nonlinear corrections to the stopping power of an electron gas for ions are analyzed, and special emphasis is made on the contribution to the stopping power coming from the excitation of single and double plasmons. Double plasmon mean free paths of swift electrons passing through an electron gas are also discussed.

Sponsors: European Space Agency; Conference code: 67919

Physical Review B, 2000

We present first-principles calculations of electron-electron scattering rates of low-energy elec... more We present first-principles calculations of electron-electron scattering rates of low-energy electrons in Au. Our full band-structure calculations indicate that a major contribution from occupied d states participating in the screening of electron-electron interactions yields lifetimes of electrons in Au with energies of 1.0-3.0 eV above the Fermi level that are larger than those of electrons in a free-electron gas by a factor of ϳ4.5. This prediction is in agreement with a recent experimental study of ultrafast electron dynamics in Au͑111͒ films ͓J. Cao et al., Phys. Rev. B 58, 10 948 ͑1998͔͒, where electron transport has been shown to play a minor role in the measured lifetimes of hot electrons in this material.

Physical Review B, 2000

First-principles calculations of the inelastic lifetime of low-energy electrons in Al, Mg, Be, an... more First-principles calculations of the inelastic lifetime of low-energy electrons in Al, Mg, Be, and Cu are reported. Quasiparticle damping rates are evaluated from the knowledge of the electron selfenergy, which we compute within the GW approximation of many-body theory. Inelastic lifetimes are then obtained along various directions of the electron wave vector, with full inclusion of the band structure of the solid. Average lifetimes are also reported, as a function of the electron energy. In Al and Mg, splitting of the band structure over the Fermi level yields electron lifetimes that are smaller than those of electrons in a free-electron gas. Larger lifetimes are found in Be, as a result of the characteristic dip that this material presents in the density of states near the Fermi level. In Cu, a major contribution from d electrons participating in the screening of electron-electron interactions yields electron lifetimes which are well above those of electrons in a free-electron gas with the electron density equal to that of valence (4s 1) electrons.

Physical Review B, 1999

The role of localized d-bands in the dynamical response of Cu is investigated, on the basis of ab... more The role of localized d-bands in the dynamical response of Cu is investigated, on the basis of ab initio pseudopotential calculations. The density-response function is evaluated in both the random-phase approximation (RPA) and a time-dependent local-density functional approximation (TDLDA). Our results indicate that in addition to providing a polarizable background which lowers the free-electron plasma frequency, d-electrons are responsible, at higher energies and small momenta, for a doublepeak structure in the dynamical structure factor. These results are in agreement with the experimentally determined optical response of copper. We also analyze the dependence of dynamical scattering cross sections on the momentum transfer.

MELECON 2006 - 2006 IEEE Mediterranean Electrotechnical Conference

ABSTRACT

2007 Joint 32nd International Conference on Infrared and Millimeter Waves and the 15th International Conference on Terahertz Electronics, 2007

Ventilator-associated pneumonia (VAP), viewed as an inevitable consequence of critical illness, i... more Ventilator-associated pneumonia (VAP), viewed as an inevitable consequence of critical illness, is increasingly accepted as an avoidable adverse health care incident. Whereas morbidity and mortality from VAP is well-documented in adults, it is poorly studied in children.This investigation was conducted to determine characteristics and possible risk factors for VAP, in critically ill neonates admitted to the neonatal intensive care unit (NICU). According to clinical pulmonary infection score (CPIS), 33 neonates were selected as having VAP and 24 neonates who did not develop VAP were assigned as non-VAP group. All neonates were subjected to case history, clinical examination, ABG, chest X-ray, and laboratory investigations (CBC, serum albumin, serum CRP, and blood culture). Neonates with VAP were subjected to broncheo-alveolar lavage (BAL) sampling. The BAL samples were subjected to macroscopic and microscopic examination, as well as quantitative cultures. Obtained results revealed that indications for mechanical ventilation (MV) included respiratory distress syndrome (RDS), congenital pneumonia, meconium aspiration syndrome (MAS), and hypoxic ischemic encephalopathy (HIE), with nonsignificant differences between VAP group and non-VAP group. VAP rates were significantly increased with decreased body weight and gestational age and with increased duration of NICU admission, duration of MV and use of invasive maneuvers. VAP was significantly associated with hypothermia, mucopurulent endotracheal tube (ETT) secretions, and radiological findings. The use of inotrops and corticosteroids was significantly noted among neonates with VAP than that among non-VAP neonates. Raised serum C-reactive protein (CRP), hypoalbuminemia and positive blood cultures were significantly associated with increased VAP rates. Cultures of BAL samples revealed Klebsiella pneumoniae (in 33%), Pseudomonas aeruginosa (in 21%), Staphylococcus aureus (in 15%), Escherichia coli (in 15%), Pneumococci (in 6%) and Candida albicans (in 9%). There was nonsignificant similarity in the type of organisms cultivated from either blood or BAL. In conclusion risk factors for the development of VAP include; 1) decreased body weight and gestational age, 2) increased duration of NICU admission, MV, and use of invasive maneuvers, 3) hypothermia, mucopurulent ETT secretions and the use of inotrops/ corticosteroids, 4) raised serum CRP, hypoalbuminemia and positive blood cultures and 5) nosocomial infection by Klebsiella, Pseudomonas, Staph aureus, E coli and Candida. [Mona Afify, Salha AI-Zahrani and Maha A Nouh. Risk Factors for the Development of Ventilator-Associated Pneumonia in Critically-Ill Neonates.

Nanotechnology in Construction 3, 2009

Calcium leaching is a degradation process consisting in the progressive dissolution of the cement... more Calcium leaching is a degradation process consisting in the progressive dissolution of the cement paste as a consequence of the migration of the calcium ions to the aggressive solution. Although the most important changes take place at the nano-and micro-scale, their consequences are observed at every length scale. Within this work, a multi-scale approach combining a wide variety of experimental techniques was used to study such phenomenon in cement pastes with silica nanoparticles. The experimental results proved that the pozzolanic reaction induced by the nanoparticles resulted in a C-S-H gel more stable chemically and with longer silicate chains. In addition, the reduction of the amount of portlandite gave place to pastes with improved microstructure. As a consequence, the performances of such pastes were greatly enhanced both before and during the degradation process.

IEEE Antennas and Propagation Society Symposium, 2004., 2004

We show that the phenomenon of extraordinary transmission though arrays of subwavelength holes is... more We show that the phenomenon of extraordinary transmission though arrays of subwavelength holes is also present in the microwave range as it occurs in the optical regime. Following simulations of the influence of the number of holes, a prototype has been designed and fabricated in an aluminum plate. By using a millimeter wave quasioptical vector network analyzer in the range between 40 GHz and 110 GHz, measurements of the transmission response have been performed. A resonant total transmission at wavelengths close to the period of the array appears in the spectra opening the possibility of exciting future applications.

2008 33rd International Conference on Infrared, Millimeter and Terahertz Waves, 2008

ABSTRACT Here, we present for the first time experimental results of the phenomenon of extraordin... more ABSTRACT Here, we present for the first time experimental results of the phenomenon of extraordinary transmission through double periodic arrays of subwavelength holes at 220 GHz. Prototypes have been designed and fabricated by deposition of a thin Aluminum layer over a polypropylene wafer. These simulation results show a resonant total transmission at wavelengths close to the long period of the array. The transmission response measurements will be performed with a Millimeter Wave Quasioptical Vector Network Analyzer in the range between 40 GHz and 260 GHz. These results can give rise to interesting applications in the emerging Metamaterials field.

2008 33rd International Conference on Infrared, Millimeter and Terahertz Waves, 2008

ABSTRACT In this work, by using an extraordinary transmission metamaterial prism and taking advan... more ABSTRACT In this work, by using an extraordinary transmission metamaterial prism and taking advance of its inherent dispersive behavior, the feasibility of manufacturing a multiplexer/demultiplexer at millimeter-wave is shown. Depending on the incoming beam frequency, the outgoing beam suffers a different deflection (governed by Snell's law). Since the frequency dependent index of refraction of this metamaterial can go from almost zero to -2 for the first propagation band, different negative outgoing angles can be obtained and then, diverse paths for each frequency, as the near-field experimental results confirm.

2009 IEEE International Workshop on Antenna Technology, 2009

Abstract A planoconcave parabolic lens exhibiting a negative index has been fabricated by using s... more Abstract A planoconcave parabolic lens exhibiting a negative index has been fabricated by using stacked subwavelength hole arrays as a route to build a metamaterial operating at millimeter wavelengths. The design consists of a staircase approximation of the ideal ...

Infrared and Millimeter Waves, Conference Digest of the 2004 Joint 29th International Conference on 2004 and 12th International Conference on Terahertz Electronics, 2004.

ABSTRACT This paper shows several possibilities for the design of metasurfaces based on etching h... more ABSTRACT This paper shows several possibilities for the design of metasurfaces based on etching holes in metallic plates, making corrugations surrounding an slit on the plate, and by introducing the concept of complementary split ring resonator. Enhanced transmission phenomena has been experimentally demonstrated in all three cases.

Physical Review B, 1998

Ab initio calculations of the electronic energy loss of ions moving in aluminum crystal are prese... more Ab initio calculations of the electronic energy loss of ions moving in aluminum crystal are presented, within linear-response theory, from a realistic description of the one-electron band-structure and a full treatment of the dynamical electronic response of valence electrons. For the evaluation of the density-response function we use the random-phase approximation and, also, a time-dependent extension of local-density functional theory. We evaluate both position-dependent and random stopping powers, for a wide range of projectile velocities. Our results indicate that at low velocities band structure effects slightly enhance the stopping power. At velocities just above the threshold velocity for plasmon excitation, the stopping power of the real solid is found to be smaller than that of jellium electrons, corrections being of about 10%. This reduction can be understood from sum rule arguments.