Open Access
Frozen mode from hybridized extraordinary transmission and Fabry-Perot resonances
(American Physical Society, 2013) Beruete Díaz, Miguel; Rodríguez Ulibarri, Pablo; Pacheco-Peña, Víctor; Navarro Cía, Miguel; Serebryannikov, Andriy E.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua, “Formación de Tecnólogos” 055/01/11. M.N.C
Frozen modes arising in stacked subwavelength hole arrays are studied in detail. Their origin is proved to be connected with the interaction between the extraordinary transmission resonance and the Fabry–Perot cavity mode. The analysis is done for various situations that differ in metal plate thicknesses and sizes and shape of the holes. Dispersion results and finite-stack transmission spectra are in good agreement, both showing the features indicating hybridization. The boundaries of the hybridization are found in terms of the geometrical parameters. The effect of the number of stacked plates on the transmission has been demonstrated. Finally, it is shown that the group index of refraction ng in the considered finite structures can be larger than 200. The obtained estimates of ng, which are based on dispersion and transmission results, well coincide with each other.
Open Access
Hedgehog subwavelength hole arrays: control over the THz enhanced transmission
(Institute of Physics Publishing, 2013) Navarro Cía, Miguel; Rodríguez Ulibarri, Pablo; Beruete Díaz, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua: 055/01/11
By backing or sandwiching a holey metal layer with or between isotropic dielectric slabs, additional peaks of transmission within the long-wavelength regime arise as a result of the induced transverse magnetic (TM) or transverse electric (TE) grounded dielectric modes. A similar control of the complex surface wave modes, and thus of the extraordinary transmission (ET) peaks, is demonstrated here via anisotropic slabs in the form of a fakir's bed of nails. However, it is shown that those ET peaks formed from TE modes are suppressed because of the inherent dispersion characteristics of the free-standing grounded pins. This allows the red-shifting of the ET for the polarization parallel to the larger in-plane period of the hole array, but unlike the dielectric isotropic slab configuration, the orthogonal polarization remains inhibited.
Open Access
Planoconcave lens by negative refraction of stacked subwavelength hole arrays
(Optical Society of America, 2008) Beruete Díaz, Miguel; Navarro Cía, Miguel; Sorolla Ayza, Mario; Campillo, Igor; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
This work presents the design of a planoconcave parabolic negative index metamaterial lens operating at millimeter wavelengths fabricated by using stacked subwavelength hole arrays. A staircase approximation to the ideal parabola profile has been done by removing step by step one lattice in each dimension of the transversal section. Theory predicts power concentration at the focal point of the parabola when the refractive index equals -1. Both simulation and measurement results exhibit an excellent agreement and an asymmetrical focus has been observed. The possibility to design similar planoconcave devices in the terahertz and optical wavelengths could be a reality in the near future.
Open Access
Far-field and near-field physics of extraordinary THz transmitting hole-array antennas
(IEEE, 2019) Camacho, Miguel; Boix, Rafael R.; Kuznetsov, Sergei A.; Beruete Díaz, Miguel; Navarro Cía, Miguel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Despite three decades of effort, predicting accurately extraordinary transmission through subwavelength hole arrays has proven challenging. The lack of quantitative design and modeling capability to take into account the inherent complexity of high frequency instrumentation has prevented the development of practical high-performance components based on this phenomenon. This paper resorts to the Method of Moments to provide not only such missing quantitative prediction but also a theoretical framework to understand and shed more light on the far-field and near-field physics of the extraordinary terahertz (THz) transmission through subwavelength hole arrays under different illumination and detection conditions. An excellent agreement between the numerical and experimental results with various illumination and detection setups is obtained, demonstrating the suitability of this computationally efficient modeling tool to predict the response of extraordinary transmission structures in practical situations.
Open Access
Wood zone plate fishnet metalens
(EDP Sciences, 2015) Orazbayev, Bakhtiyar; Beruete Díaz, Miguel; Navarro Cía, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Fresnel-zone plate lenses provide focusing performance while having low profile. Unfortunately, they usually display higher reflection losses than conventional dielectric lenses. Here, we demonstrate a low-profile Wood zone plate metalens based on the fishnet metamaterial working in a near-zero regime with an equivalent refractive index less than unity (nf = 0.51). The metalens is made of alternating dielectric and fishnet metamaterial concentric rings. The use of fishnet metamaterial allows reducing the reflections from the lens, while maintaining low profile, low cost and ease of manufacturing. The lens is designed towork at theW-band of the millimeter-waves range with a focal length FL = 22.8 mm (7.5 λ0) aiming at antenna or radar system applications. The focusing per- formance of the lens along with its radiation characteristics in a lens antenna configuration have been studied numerically and confirmed experimentally, showing a gain improvement of ~2.5 dB with respect to a fishnet Soret metalens.
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
Millimeter-wave phase resonances in compound reflection gratings with subwavelength grooves
(Optical Society of America, 2010) Beruete Díaz, Miguel; Navarro Cía, Miguel; Skigin, Diana C.; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Experimental evidence of phase resonances in a dual-period reflection structure comprising three subwavelength grooves in each period is provided in the millimeter-wave regime. We have analyzed and measured the response of these structures and show that phase resonances are characterized by a minimum in the reflected response, as predicted by numerical calculations. It is also shown that under oblique incidence these structures exhibit additional phase resonances not present for normal illumination because of the potentially permitted odd field distribution. A satisfactory agreement between the experimental and numerical reflectance curves is obtained. These results confirm the recent theoretical predictions of phase resonances in reflection gratings in the millimeter-wave regime, and encourage research in this subject due to the multiple potential applications, such as frequency selective surfaces, backscattering reduction and complex-surface-wave-based sensing. In addition, it is underlined here that the response becomes much more complex than the mere infinite analysis when one considers finite periodic structures as in the real experiment.
Open Access
A slow light fishnet-like absorber in the millimeter-wave range
(EMW Publishing, 2011) Navarro Cía, Miguel; Torres Landívar, Víctor; Beruete Díaz, Miguel; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A novel route to achieve a narrowband free-space electromagnetic absorber in any range of the spectrum based on stacked subwavelength hole arrays is proposed. The absorption is obtained by means of a slow light mode inside a fishnet-like engineered structure and exploiting the unavoidable misalignments and bucklings of the free-standing stack. An incoming pulse becomes permanently trapped in the structure due to the near zero group velocity which causes an enhancement of the radiation-structure interaction that leads to a huge increment of losses arising from the finite conductivity of the metal as well as arrangement tolerances. This approach is studied not only by simulation but also experimentally under normal incidence at millimeter wavelengths. Moreover, a basic grasp about the angular dependence of the structure is given by analyzing the 2D dispersion diagram. It shows that this scheme may also display high absorption under oblique incidence for s-polarization (or TE-polarization), whereas p-polarization (TM-polarization) would degrade its performance.
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.