Open Access
New regimes to achieve enhanced transmission through subwavelength hole arrays
(2011) Navarro Cía, Miguel; Beruete Díaz, Miguel; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this communication we present millimetre- and THz-waves experimental confirmation of enhanced transmission through subwavelength hole arrays with rectangular lattice when the incident electric field is parallel to the short periodicity.
Open Access
Millimeter-wave extraordinary transmission: connection to metamaterials and technological applications
(2006) Beruete Díaz, Miguel; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The phenomenon of Enhanced Transmission also happens in the millimeter wave range, as it happened in optical frequencies. This experimental fact shows that this is a phenomenon mostly linked to the periodic structure regardless of the model used to describe the metal. The number of illuminated holes is a key parameter to observe the Enhanced Transmission band. Measurements in Fresnel zone show a weak band, and with the farfield illumination a good level is obtained. It has been shown that ET is mainly governed by one of the transversal periodicities, the one in the direction of the electric field (under normal incidence). The presence of dielectrics can produce a great field confinement and therefore a more efficient illumination of holes. Enhancement of transmission through a narrow slot on a metallic plane achieved by corrugating the metallic plane has been experimentally proven in the range of microwaves and millimeter waves. This result links the enhancement to the geometry of the metallic substrate rather than to the metallic model. It has been checked the ability to produce a strong beaming at broadside in the configuration of corrugations drilled on the output face. Several low-profile and all-metallic antenna prototypes have been designed and measured in the microwave range. The feeding is made by means of a waveguide. By changing the central (ideally) infinite slit to a finite slot several improvements can be done, fundamentally the thickness of the antenna can be reduced and a dual-band operation can be achieved. A great variety of farfield characteristics can be obtained by changing the number of corrugations. High gain antennas can be attained by using annular corrugations, the socalled Bull’s-Eye antenna. Further improvements deal with the insertion of dielectric inside the corrugations and with changes in the shape of the corrugations, for example sinusoidal profile. An artificial waveguide defined by introducing a set of parallel electric and magnetic conductors can be employed to analyze the diffraction problem of an incident plane wave normally to a sub-wavelength hole array. Evanescent higher order modes play a key role in the ET effect. Even more unexpected results appear if a periodic structure is made by stacking several of such plates: a left-handed metamaterial can be achieved by the periodic stacking of sub-wavelength hole array plates to form a photonic band-gap structure. The stack period with LH behavior can be made much smaller than the operating wavelength, and therefore it can be safely stated that the structure works in that dimension as an effective metamaterial. Simulation and experimental results presented show that left-handed propagation effects appearing in the band where EOT happens can be allowed or inhibited by a proper engineering of the band gap position of the photonic crystal made of stacked subwavelength hole-arrays. In the transition from LH to RH behavior a nearly zero slope band is observed, which can evidence a frozen mode propagation regime inside the structure. A simplified model based on inverse line equivalent circuit has been exposed to explain the LH and RH behavior. The stacked hole array structure can be engineered to construct prisms with anomalous behavior. Other geometries such as parabolic lenses can also be achieved. It has been seen that surfaces made by the periodical arrangement of Split- Ring Resonators (SRRs) and its complementary particle (CSRRs) illuminated by a plane wave show a high variety of cross-polarization effects. The analytical discussion based on the homogenization principle has been compared with the experimental results. It is able to catch the qualitative features in the response of the screens. The complementarity in the response of SRRs and CSRRs has been checked. Applications of the studied devices to frequency selective surfaces, polarizers and polarization converters can be envisaged. The existence of electroinductive waves (EIWs) in chains of electrically coupled CSRRs has been demonstrated both theoretically and experimentally. The duality between EIWs and previously reported MIWs has been discussed, and the ability of long CSRR chains to transport electromagnetic energy along many periods has been shown. A practical transducer between electromagnetic and EIWs in planar technology has been proposed and analyzed. Regarding practical applications, EIWs can be an alternative to MIWs for the guidance of electromagnetic energy, as well as for the design of couplers, delay lines and other planar devices, when electric couplings rather than magnetic couplings are imposed, or simply desired for the design. Taking as a basis the resonators used to implement an EI waveguide, a further step has been given in the design of a UWB filter in microstrip technology. This filter can be improved by inserting CSRRs to reject the higher frequencies. A final word fundamentally related to the ET results presented here: The reported results have been achieved for the millimetre range, but similar results are expected to happen at optical frequencies since extraordinary transmission has been shown at optical frequencies and the kind of structure presented here will present low losses in higher frequency regime. The control of the EOT-LHM could lead to a new class of practical devices both in the microwave and in the optical range.
Open Access
The beauty of anisotropy in extraordinary transmission fishnet metamaterials
(2011) Navarro Cía, Miguel; Beruete Díaz, Miguel; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this work, we explore both numerically and experimentally, the possibility to obtain positive and negative refraction regimes that depend on the wave polarization, exploiting the strong anisotropy of extraordinary transmission fishnet metamaterials.
Open Access
Blind spot mitigation in phased array antenna using metamaterials
(IEEE, 2014) Crépin, Thomas; Martel, Cédric; Gabard, Benjamin; Boust, Fabrice; Martinaud, Jean-Paul; Dousset, Thierry; Rodríguez Ulibarri, Pablo; Beruete Díaz, Miguel; Loecker, Claudius; Bertuch, Thomas; Marcotegui Iturmendi, José Antonio; Maci, Stefano; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this work, a metaradome based on a fakir’s bed of nails is designed and tested in order to suppress the blind directions of a 100-element antenna array. The antenna is a microstrip array designed to operate in X-band. The fakir’s bed metamaterial-like was first approximated using analytical formulas before a full-wave numerical optimization. Experimental results are exposed and confronted to numerical results. They show a significant reduction of the blind spot subsequent to the metaradome addition.
Open Access
Comportamiento de propagacion electromagnetica en el apilamiento de agujeros sublambda y agujeros propagantes
(2009) Navarro Cía, Miguel; Beruete Díaz, Miguel; Falcone Lanas, Francisco; Campillo, Igor; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this work, we provide more insight on the physics underlying the transmission through subwavelength hole arrays metaprism by comparing it with propagating hole arrays prism. We show the critical role that the size of the holes plays in this electromagnetic propagation, changing the effective index of refraction from negative to positive values as the hole diameter increases. This causes negative refraction for the zero-th order emerging beam in the metaprism whereas positive refraction in the non-cut-off holes prism. Experimental results (co- and cross-polar measurements) performed at the V-band of the millimeter waves in the Fresnel zone are well supported by numerical analyses in terms of dispersion diagram, spatial electric field distribution and power flow within the prism along with in the output air zone. As expected, higher order diffracted outgoing beams are recorded for the classical prism but not for the metaprism.
Open Access
Analysis of surface-plasmon-like modes under an engineering perspective
(2011) Navarro Cía, Miguel; Beruete Díaz, Miguel; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this communication we show how one can exploit equivalent circuits to analyze surface-plasmon-like modes (slit and hole arrays, Sievenpiper mushrooms and coaxial hole arrays) and to propose new designs with outstanding features.
Open Access
Lentes metálicas basadas en el fenómeno de transmisión extraordinaria para conseguir índices de refracción negativos
(2009) Navarro Cía, Miguel; Beruete Díaz, Miguel; Sorolla Ayza, Mario; Campillo, Igor; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this communication we report plano-concave and bi-concave metamaterial lenses based on the close stack of subwavelegnth hole arrays. Contrary to what is expected from cut-off holes, an engineered array of holes supports Extraordinary Transmission. Moreover, the medium formed when those structures are subwavelength stacked (thus, under metamaterial condition) behaves as a medium with effective negative index of refraction, which allows designing new lenses with properties that were only guessed at not long ago such as perfect imaging, subdiffraction and free-space matching to name a few.
Open Access
Liquid crystals in reconfigurable reflectarray antennas for sub-millimeter waves
(IEEE, 2024-08-21) Pérez Quintana, Dayan; Aguirre Gallego, Erik; Olariaga Jauregui, Eduardo; Kuznetsov, Sergei A.; Lapanik, Valeri I.; Sutormin, Vitaly S.; Zyryanov, Victor Ya; Marcotegui Iturmendi, José Antonio; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
Accelerated technological progress responds to the dynamic evolution of wireless communication systems, fueled by the advent of 5G, the emergence of 6G, and the pervasive integration of the IoT paradigm. Smart antennas play a pivotal role in this advancement, facilitating electronic beam steering to meet escalating demands for enhanced bandwidth and elevated operating frequencies. The spotlight shifts to reconfigurable reflectarray antennas, gaining prominence over conventional phased arrays. Notably, liquid crystals (LCs) emerge as a promising avenue for creating electronically reconfigurable/switchable reflectarrays, specifically tailored for short millimeter and terahertz waves. LCs, as a unique aggregate state combining solid and liquid features, address current technology limitations. Their uniaxial nature and the ability to manipulate molecule orientation enable effective fine-tuning of dielectric permittivity without drawbacks present in existing technologies.
Open Access
Dielectric sensing of deeply subwavelength analytes using epsilon-near-zero waveguides
(IEEE, 2024-10-08) Lezaun Capdevila, Carlos; Pacheco-Peña, Víctor; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
The advent of metamaterials brought new wave-matter interaction paradigms to manipulate field and waves at will. Their applications are numerous: antennas, lenses, invisibility cloaking, computing, vortex beams and more. In turn, epsilon-near-zero (ENZ) metamaterials opened up new phenomena for light manipulation due to their exotic propagation constant, wavenumber and characteristic impedance. In 2008, it was demonstrated that a rectangular waveguide can emulate ENZ media by working near the cutoff frequency [1]. Moreover, the incredible field confinement inside the ENZ waveguide provided interesting features for sensing applications [2]. Our work further develops the idea of a dielectric body sensor based on a ENZ waveguide by considering an analyte partially filling the waveguide [3] and demonstrating empirically the setup [4].
Open Access
Artificial intelligence-enhanced metamaterial bragg multilayers for radiative cooling
(Wiley, 2024-10-08) Osuna Ruiz, David; Aznárez-Sanado, Maite; Herrera, Pilar; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Gobierno de Navarra / Nafarroako Gobernua
A full numerical study combining artificial intelligence (AI) methods and electromagnetic simulation software on a multilayered structure for radiative cooling (RC) is investigated. The original structure is made of SiO2/Si nanometer-thick layers that make a Bragg mirror for wavelengths in the solar irradiance window (0.3–4 μm). The structures are then optimized in terms of the calculated net cooling power and characterized via the reflected and absorbed incident light as a function of their structural parameters. This investigation provides with optimal designs of beyond-Bragg, all-dielectric, ultra-broadband mirrors that provide net cooling powers in the order of ≈100 W m−2, similar to the best-performing structures in literature. Furthermore, it explains AI's success in producing these structures and enables the analysis of resonant conditions in metal-free multilayers with unconventional layer thickness distributions, offering innovative tools for designing highly efficient structures in RC.