Open Access
Experimental demonstration of deeply subwavelength dielectric sensing with epsilon-near-zero (ENZ) waveguides
(American Institute of Physics, 2022) Beruete Díaz, Miguel; Engheta, Nader; Pacheco-Peña, Víctor; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
In this Letter, an all metallic sensor based on ε-near-zero (ENZ) metamaterials is studied both numerically and experimentally when working at microwave frequencies. To emulate an ENZ medium, a sensor is made by using a narrow hollow rectangular waveguide, working near the cutoff frequency of its fundamental TE 10 mode. The performance of the sensor is systematically evaluated by placing subwavelength dielectric analytes (with different sizes and relative permittivities) within the ENZ waveguide and moving them along the propagation and transversal axes. It is experimentally demonstrated how this ENZ sensor is able to detect deeply subwavelength dielectric bodies of sizes up to 0.04λ and height 5 × 10 −3 λ with high sensitivities (and the figure of merit) up to 0.05 1/RIU (∼0.6 1/GHz) and 0.6 1/RIU when considering the sensor working as a frequency- or amplitude-shift-based device, respectively.
Open Access
Response of complementary split ring resonators in composite stratified substrate integrated waveguide
(American Institute of Physics, 2017) Pérez Escudero, José Manuel; Jarauta Ayensa, Eduardo; Falcone Lanas, Francisco; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
In this work, the behavior of a Complementary Split Ring Resonator (CSRR) operating within the quasi-static resonance regime and embedded in a composite stratified Substrate Integrated Waveguide (SIW) with two different dielectric layers is analyzed. In these conditions, the propagating modes within the SIW combined with the imposed non-symmetrical structure lead to the excitation of the CSRR elements inside the SIW at difference with conventional excitation. Several cases of CSRR loaded SIW are proposed, and their electromagnetic field components as well as their frequency response are analyzed, providing insight into the CSRR resonance excitation. A test prototype has been designed, fabricated, and measured, showing a good agreement with simulation results and providing a new alternative for the implementation of compact frequency selective devices compatible with planar technology and without undesired radiation loss.
Open Access
Compact bull's-eye antenna in ridge gap waveguide with circular polarization at 60 GHz
(IEEE, 2021) Pérez Quintana, Dayan; Ederra Urzainqui, Íñigo; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
In this work, a Bull's-Eye (BE) antenna with circular polarization (CP) based on ridge gap waveguide (RGW) technology, working in the millimeter-wave band (60 GHz) is numerically and experimentally demonstrated. The structure is coupled through a step transition to a ridge-line that ends in two orthogonal arms of different lengths to generate CP. The wave is coupled to the top plate by a central diamond slot surrounded by the BE structure, which consists of four concentric periodic corrugations around the slot. Simulations and experimental results are in good agreement, with practical bandwidth of 6.8% with respect to center frequency and peak gain of 18.4 dB. The antenna has right-handed CP (RHCP) with polarization discrimination of more than 30 dB.
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
Electroinductive waves in chain of complementary metamaterial elements
(AIP Publishing, 2006) Beruete Díaz, Miguel; Falcone Lanas, Francisco; Freire, M. J.; Marqués, R.; Baena, J.D.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Electronductive waves supported by chains of resonators drilled on a metallic plate are presented. Propagation of energy comes as a consequence of the electric coupling between these resonators. Therefore, these waves are termed as electroinductive waves. They can be interpreted as the dual counterpart of the so-called magnetoinductive waves, which are due to the mutual inductances along chains of resonators. In order to show their existence, some electromagnetic simulations and experiments have been carried out, using as resonators the complementary particle of the split ring resonator. The reported result opens the way to a high variety of applications in one- and two-dimensional devices, such as transducers, delay lines, bends, power dividers, couplers, antennas, lenses, etc.
Open Access
Metal 3D printed D-Band waveguide to surface wave transition
(IEEE, 2020) Freer, Suzanna; Martinez, Rafael; Pérez Quintana, Dayan; Beruete Díaz, Miguel; Hanham, Stephen M.; Attallah, Moataz M.; Navarro Cía, Miguel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
The coupling efficiency between free space waves and surface waves is low, narrowband, or both. Highly efficient broadband (better than 20% fractional bandwidth) coupling from waveguide modes can be achieved through sophisticated transitions whose fabrication can be enabled through additive manufacturing (e.g. selective laser melting). Here, we present alternative metallic transitions designed to couple the fundamental mode of a D-band waveguide to the fundamental transversemagnetic surface mode supported by a periodic metal corrugated grating. Simulations of the coupling process and initial measurements have been undertaken.
Open Access
Angle-susceptible sensing metasurface in terahertz regime
(EDP Sciences, 2018) Nikolaev, Nazar A.; Kuznetsov, Sergei A.; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Nowadays thin-film coatings and structures are widely used in advanced industrial and scientific ap-plications that makes the tasks of thin-film sensing highly demanded in practice. Last decade, stimulated by progress in terahertz (THz) instrumentation, a keen interest has been attracted to the THz spectral range to develop its potential for detecting and measuring properties of thin films. The THz radiation can be an alternative to visible and IR waves when examining optically opaque coatings. Meanwhile, due to a rela-tively large wavelength λ, the conventional spectro-scopic methods (TDS-, FDS-, FTIR-, BWO-based) are ill-suited for direct characterization of films with the thickness d of about 2−4 orders of magnitude smaller than λ. This problem can be solved with met-amaterials, in particular, with plasmonic metasurfaces (PMSs) [1–5]. The plasmonic resonance exhibits a high sensitivity of its spectral response to the dielec-tric environment due to a strong field localization what makes possible measuring of analyte layers sat-isfying d << λ condition. The traditional approach of THz thin-film sensing with PMSs is based on detecting a frequency shift of the resonance when the analyte is deposited onto the PMS. In this work, we present the idea to substitute THz spectral measurements for tracking the PMS re-sponse at a fixed wavelength upon changing the incidence angle θ of the exciting THz beam. This concept works well for the PMS with a narrowband resonance sensitive to θ. The results of the numerical investigations and experimental study of such PMS designed as a single-layer array of hexagon-shaped annular slots (Fig. 1) with angle-susceptible resonant transmission near 0.85 THz are presented.
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
Enhancing the infrared and visible emission properties of calcium silicate hydrate for radiative cooling using metamaterials
(IEEE, 2022) Lezaun Capdevila, Carlos; Dolado, Jorge S.; Torres García, Alicia E.; Pérez Escudero, José Manuel; Liberal Olleta, Íñigo; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Two periodic structures composed of metal cylinders with different orientations are used to improve the solar reflection of calcium silicate hydrate (CSH) while maintaining its atmospheric emission. Interesting effects have been found when the distance between bars is small, suggesting that lattice effects, arising from the interaction between the rods could be leveraged in the design of these metamaterials. The size of the metal bars is selected based on state of the art micro-manufacturing techniques. This study limits its scope to a CSH gel model; i.e. the most important component of cement-based materials. Further research will be undertaken to consider a best description of the dielectric function of concrete.
Embargo
Terahertz sensing based on metasurfaces
(Wiley, 2020) Beruete Díaz, Miguel; Jáuregui López, Irati; Institute of Smart Cities - ISC
The terahertz (THz) band has very attractive characteristics for sensing and biosensing applications, due to some interesting features such as being a non-ionizing radiation, very sensitive to weak interactions, thus, complementing typical spectroscopy systems in the infrared. However, a fundamental drawback is its relatively long wavelength (10–1000 µm) which makes it blind to small features, hindering seriously both thin-film and biological sensing. Recently, new ways to overcome this limitation have become possible thanks to the advent of metasurfaces. These artificial structures are planar screens usually made of periodic metallic resonators and whose electromagnetic response can be controlled at will by design. This design freedom allows metasurfaces to surpass the restrictions of classical THz spectroscopy, by creating fine details comparable to the size of the thin films or microorganisms under test. The strong field concentration near these small metasurface details at resonance makes them highly sensitive to tiny variations in the nearby environment, allowing for an enhanced detection more accurate than classical THz spectroscopy. The main advances in THz metasurface sensors from a historical as well as application-oriented perspective are summarized. The focus is put mainly on thin-film and biological sensors, with an aim to cover the most recent advances in the topic.