Open Access
Revealing the underlying mechanisms behind TE extraordinary THz transmission
(Chinese Laser Press, 2020) Freer, Suzanna; Camacho, Miguel; Kuznetsov, Sergei A.; Boix, Rafael R.; Beruete Díaz, Miguel; Navarro Cía, Miguel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Transmission through seemingly opaque surfaces, so-called extraordinary transmission, provides an exciting plat- form for strong light–matter interaction, spectroscopy, optical trapping, and color filtering. Much ofthe effort has been devoted to understanding and exploiting TM extraordinary transmission, while TE anomalous extraordinary transmission has been largely omitted in the literature. This is regrettable from a practical point ofview since the stronger dependence ofthe TE anomalous extraordinary transmission on the array’s substrate provides additional design parameters for exploitation. To provide high-performance and cost-effective applications based on TE anomalous extraordinary transmission, a complete physical insight about the underlying mechanisms ofthe phe- nomenon must be first laid down. To this end, resorting to a combined methodology including quasi-optical terahertz (THz) time-domain measurements, full-wave simulations, and method ofmoments analysis, subwave- length slit arrays under s-polarized illumination are studied here, filling the void in the current literature. We believe this work unequivocally reveals the leaky-wave role of the grounded-dielectric slab mode mediating in TE anomalous extraordinary transmission and provides the necessary framework to design practical high-performance THz components and system
Open Access
Broadband spoof plasmons and subwavelength electromagnetic energy confinement on ultrathin metafilms
(Optical Society of America, 2009) Navarro Cía, Miguel; Beruete Díaz, Miguel; Agrafiotis, Spyros; Falcone Lanas, Francisco; Sorolla Ayza, Mario; Maier, Stefan A.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A complementary split ring resonator (CSRR)-based metallic layer is proposed as a route to mimic surface plasmon polaritons. A numerical analysis of the textured surface is carried out and compared to previous prominent topologies such as metal mesh, slit array, hole array, and Sievenpiper mushroom surfaces, which are studied as well from a transmission line perspective. These well-documented geometries suffer from a narrowband response, alongside, in most cases, metal thickness constraint (usually of the order of λ/4) and non-subwavelength modal size as a result of the large dimensions of the unit cell (one dimensions is at least of the order of λ/2). All of these limitations are overcome by the proposed CSRR-based surface. Besides, a planar waveguide is proposed as a proof of the potential of this CSRR-based metallic layer for spoof surface plasmon polariton guiding. Fundamental aspects aside, the structure under study is easy to manufacture by simple PCB techniques and it is expected to provide good performance within the frequency band from GHz to THz.
Open Access
Polarization-tunable negative or positive refraction in self-complementariness-based extraordinary transmission prism
(EMW Publishing, 2010) Navarro Cía, Miguel; Beruete Díaz, Miguel; Falcone Lanas, Francisco; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Here we report a prism made of stacked quasi-selfcomplementary extraordinary transmission surfaces which allows simultaneously left- and right-handed propagation within the V-band for vertical and horizontal polarizations, respectively and righthanded propagation within the W-band for both polarizations. The numerical dispersion diagram of the infinite structure and effective indexes of refraction retrieved from S-parameters under normal incidence together with the finite integration time domain simulations predict single negative and double positive birefringence. The unusual type of birefringence single negative and regular double positive birefringence are afterwards demonstrated experimentally at the millimeter-waves (V- and W-bands) by the wedge experiment which lets us check, using a straightforward geometrical method, the refraction of each component. The effective index of refraction is retrieved via the Snell's law and compared to those obtained through the dispersion diagram and the retrieval method from S-parameters computed with the commercial software CST Microwave StudioTM.
Restricted
Efectos de interacción EBG/Metamateriales en tecnología plana de microondas
(2006) Navarro Cía, Miguel; Escuela Técnica Superior de Ingenieros Industriales y de Telecomunicación; Telekomunikazio eta Industria Ingeniarien Goi Mailako Eskola Teknikoa; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Open Access
Compact dual-band terahertz quarter-wave plate metasurface
(IEEE, 2014) Torres Landívar, Víctor; Etayo Salinas, David; Ortuño Molinero, Rubén; Navarro Cía, Miguel; Beruete Díaz, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A dual-band quarter-wave plate based on a modified extraordinary transmission hole array is numerically analyzed and experimentally demonstrated at terahertz frequencies. To control independently orthogonal polarizations, the original square holes are connected with vertical slits and their lateral straight sides are replaced by meander lines. This smart design enables dual-band operation with unprecedented fractional bandwidths in a compact structure. Considering a flattening deviation lower than 40% of the optimum value, a fractional bandwidth of 53.8% and 3.8% is theoretically obtained (16.8% and 2.9% in the experiment) at 1 and 2.2 THz, respectively. At these two frequencies, the structure is 0.13-λ and 0.29-λ thick, respectively. Given the compactness of the whole structure and the performance obtained, this quarter-wave plate is presented as a competitive device for the terahertz band.
Open Access
ε-near-zero (ENZ) graded index quasi-optical devices: steering and splitting millimeter waves
(IOP Publishing, 2014) Pacheco-Peña, Víctor; Torres Landívar, Víctor; Beruete Díaz, Miguel; Navarro Cía, Miguel; Engheta, Nader; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Graded index ε near-zero (GRIN-ENZ) quasi-optical components such as beam steerers and power splitters are designed, simulated and analyzed. The GRIN-ENZ medium is realized using stacked narrow hollow waveguides whose infinite array shows the first transmission peak at 1.0002 THz. Several GRIN-ENZ beam steerers to channel a normal incident plane wave to different output angles (15, 45, 65 and 80 deg) with good impedance matching (low reflection) are analytically and numerically demonstrated using planar structures with a thickness of 5λ0 = 1500 μm along z-axis. Moreover, symmetrical and asymmetrical power splitters are designed with output angles (plus/minus 45 deg) and (-80, +35 deg), respectively.
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
Exploiting the dispersion of the double-negative-index fishnet metamaterial to create a broadband low-profile metallic lens
(Optical Society of America, 2015) Orazbayev, Bakhtiyar; Pacheco-Peña, Víctor; Beruete Díaz, Miguel; Navarro Cía, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Metamaterial lenses with close values of permittivity and permeability usually display low reflection losses at the expense of narrow single frequency operation. Here, a broadband low-profile lens is designed by exploiting the dispersion of a fishnet metamaterial together with the zoning technique. The lens operates in a broadband regime from 54 GHz to 58 GHz, representing a fractional bandwidth ~7%, and outperforms Silicon lenses between 54 and 55.5 GHz. This broadband operation is demonstrated by a systematic analysis comprising Huygens-Fresnel analytical method, full-wave numerical simulations and experimental measurements at millimeter waves. For demonstrative purposes, a detailed study of the lens operation at two frequencies is done for the most important lens parameters (focal length, depth of focus, resolution, radiation diagram). Experimental results demonstrate diffraction-limited ~0.5λ transverse resolution, in agreement with analytical and numerical calculations. In a lens antenna configuration, a directivity as high as 16.6 dBi is achieved. The different focal lengths implemented into a single lens could be potentially used for realizing the front end of a non-mechanical zoom millimeter-wave imaging system.
Open Access
Low-sidelobe-level millimeter-wave asymmetric bull's eye antenna with minimal profile feeding
(IEEE, 2024) Navarro Cía, Miguel; Beaskoetxea Gartzia, Unai; Teniente Vallinas, Jorge; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Bull’s eye antennas exhibit remarkable directivity considering their low profile, albeit accompanied by high sidelobes. This undesirable radiation characteristic is tackled here by reporting a complementary split ring feeding whereby the broadside space-wave partially responsible for the high sidelobes is cancelled while the leaky wave is excited effectively. This feeding results in an asymmetric bull’s eye antenna with minimal profile (∼ 0.73λ0) and no protrusions on the radiating interface. The fabricated 10-period antenna operating in the Ka-band shows a directivity of 23.5 dBi, a sidelobe level of −22.9 dB (>6 dB improvement compared to other bull’s eye antennas) and a beamwidth of 3.7◦ and 6.7◦ in the E- and H-plane, respectively.
Open Access
Circuit approach to the minimal configuration of terahertz anomalous extraordinary transmission
(American Institute of Physics, 2011) Beruete Díaz, Miguel; Navarro Cía, Miguel; Kuznetsov, Sergei A.; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this letter we present an in-depth circuit analysis of anomalous extraordinary transmission ET through subwavelength slit and hole arrrays loaded by a dielectric slab. We show the key role played by the thickness of the dielectric slab in order to enhance the transmission for TE-polarized waves incident electric field parallel to the slits or to the short in-plane period in hole arrays arranged in rectangular lattice within the cut-off regime of the apertures and to suppress Wood’s anomaly. Analytical and numerical results together with experimental data are presented, showing good agreement among them. This work provides physical insight of the underlying mechanism governing anomalous ET and offers further independent control over orthogonal polarized waves impinging into subwavelength aperture arrays.