Open Access
One-way quasiplanar terahertz absorbers using nonstructured polar dielectric layers
(American Physical Society, 2017) Rodríguez Ulibarri, Pablo; Serebryannikov, Andriy E.; Beruete Díaz, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A concept of quasiplanar one-way transparent terahertz absorbers made of linear isotropic materials is presented. The resulting structure consists of a homogeneous absorbing layer of polar dielectric, GaAs, a dispersion-free substrate, and an ultrathin frequency-selective reflector. It is demonstrated that perfect absorption can be obtained for forward illumination, along with total reflection at backward illumination and transparency windows in the adjacent bands. The design is particularized for the polaritonic gap range where permittivity of GaAs varies in a wide range and includes epsilon-near-zero and transparency regimes. The underlying physics can be explained with the aid of a unified equivalent-circuit (EC) analytical model. Perfect matching of input impedance in forward operation and, simultaneously, strong mismatch in the backward case are the universal criteria of one-way absorption. It is shown that perfect one-way absorption can be achieved at rather arbitrary permittivity values, provided these criteria are fulfilled. The EC results are in good agreement with full-wave simulations in a wide range of material and geometrical parameters. The resulting one-way absorbers are very compact and geometrically simple, and enable transparency in the neighboring frequency ranges and, hence, multifunctionality that utilizes both absorption- and transmission-related regimes.
Open Access
Multiband one-way polarization conversion in complementary split-ring resonator based structures by combining chirality and tunneling
(Optical Society of America, 2015) Serebryannikov, Andriy E.; Beruete Díaz, Miguel; Mutlu, Mehmet; Ozbay, Ekmel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Multiband one-way polarization conversion and strong asymmetry in transmission inspired by it are demonstrated in ultrathin sandwiched structures that comprise two twisted aperture-type arrays of complementary split-ring resonators (CSRRs), metallic mesh, and dielectric layers. The basic features of the resulting mechanism originate from the common effect of chirality and tunneling. The emphasis is put on the (nearly) perfect polarization conversion of linear incident polarization into the orthogonal one and related diodelike asymmetric transmission within multiple narrow bands. Desired polarization conversion can be obtained at several resonances for one of the two opposite incidence directions, whereas transmission is fully blocked for the other one. The resonances, at which the (nearly) perfect conversion takes place, are expected to be inherited from similar structures with parallel, i.e., not rotated CSRR arrays that do not enable chirality and, thus, polarization conversion. It is found that the basic transmission and polarization conversion features and, thus, the dominant physics are rather general, enabling efficient engineering of such structures. The lowest-frequency resonance can be obtained in structures made of conventional materials with total thickness less than λ 50/ and up to ten such resonances can correspond to thickness less than λ 20/ .
Open Access
Evolutionary algorithms applied to multi-layered radiative cooling metamaterials
(IEEE, 2022) Lezaun Capdevila, Carlos; Jorajuria Gómez, Tania; Torres García, Alicia E.; Herrera, Pilar; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
A newly design method for designing multi-layered radiative cooling metamaterials based on genetic algorithms (GAs) is exposed. The developed GA has been tested in three cases, resulting in three different structures that achieve, theoretically under direct sunlight, a net cooling power of 39.96 W/m 2 , 57.78 W/m 2 and 61.77 W/m 2 . Such devices are composed of 9, 15 and 24 layers respectively with a total thickness of less than 4.8 µm in the worst case. By the nature of the method, fewer design experience in metamaterials is needed, as well as it is free-cost, due to the use of analytical calculations for the emissivity of the meta materials instead of a commercial generic electromagnetic solver. Automated design of radiative cooling multi-layered structures and other applications in the infrared range can be further developed with this work.
Open Access
Application of MIR spectroscopy to the evaluation of chemical composition and quality parameters of foal meat: a preliminary study
(MDPI, 2020) Ruiz Darbonnens, Marta; Beriain Apesteguía, María José; Beruete Díaz, Miguel; Insausti Barrenetxea, Kizkitza; Lorenzo, José M.; Sarriés Martínez, María Victoria; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD
The aim of this work was to study the potential of mid-infrared spectroscopy to evaluate the chemical composition and quality parameters of foal meat according to differences based on slaughter ages and finishing diets. In addition, the wavelength ranges which contribute to this meat quality differentiation were also determined. Important characteristics as moisture and total lipid content were well predicted using Mid-Infrared Spectroscopy (MIR) with Rv2 values of 82% and 66%, respectively. Regarding fatty acids, the best models were obtained for arachidonic, vaccenic, docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) with Rv2 values over 65%. Quality parameters, as instrumental colour and texture and sensory attributes did not reach high prediction coefficients (R2). With the spectra data of the region 2198–1118 cm-1, samples were accurately classified according to slaughter age (78%) and finishing diet (72%). This preliminary research shows the potential of MIR spectroscopy as an alternative tool to traditional meat chemical composition methods. Finally, the wavelength range of the spectrum from 2198 to 1118 cm-1 showed good results for classification purposes.
Open Access
Terajets produced by dielectric cuboids
(AIP Publishing, 2014) Pacheco-Peña, Víctor; Beruete Díaz, Miguel; Minin, Igor V.; Minin, Oleg V.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The capability of generating terajets using three-dimensional (3D) dielectric cuboids working at terahertz (THZ) frequencies (as analogues of nanojets in the infrared band) is introduced and studied numerically. The focusing performance of the terajets is evaluated in terms of the transversal full width at half maximum (FWHM) along x- and y-directions using different refractive indices for a 3D dielectric cuboid with a fixed geometry, obtaining a quasi-symmetric terajet with a subwavelength resolution of 0.46 wavelengths when the refractive index is n=1.41. Moreover, the backscattering enhancement produced when metal particles are introduced in the terajet region is demonstrated for a 3D dielectric cuboid and compared with its two-dimensional (2D) counterpart. The results of the jet generated for the 3D case are experimentally validated at sub-THZ waves, demonstrating the ability to produce terajets using 3D cuboids.
Open Access
Lipid and protein oxidation marker compounds in horse meat determined by MIR spectroscopy
(MDPI, 2020) Jáuregui López, Irati; Zulategui Beñarán, Fernando; Beriain Apesteguía, María José; Sarriés Martínez, María Victoria; Beruete Díaz, Miguel; Insausti Barrenetxea, Kizkitza; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD
This work broadens the study of lipid and protein oxidation marker compounds in foal meat, employing the technology of Attenuated Total Reflectance-Fourier Transform Mid-Infrared Spectroscopy (ATR-FT/MIR, shortened in the following as MIR). As a main objective, marker compounds from 23 foals were extracted and their absorbance spectra were measured to establish prediction models (calibration and validation) between them and classical quantification analysis of the compounds. Another objective was to ascertain whether a previous extraction of the marker compounds before executing their MIR analysis is preferable compared to direct MIR measurements on the raw meat samples. In this context, marker compound results (TBARS between 0.4387 and 2.1040, and carbonyls between 4.07 and 4.68) showed more consistent predictive models than the ones achieved using quantitative analysis of the spectra obtained from the raw meat. Lipid oxidation compounds predictive models obtained in this work offered an R-cv(2) of 63.18% and protein oxidation R-cv(2) obtained in this project showed a value of 54.24%. Thus, MIR technology arises as a promising tool to identify and quantify products derived from lipid and protein oxidation in fresh foal meat.
Open Access
Ku band low profile asymmetric Bull’s-Eye antenna with reduced side lobes and monopole feeding
(IEEE, 2018) Beaskoetxea Gartzia, Unai; Torres García, Alicia E.; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
In this paper, a linearly polarized low profile and asymmetric Bull’s-Eye leaky wave antenna fed by a monopole operating at 13 GHz is presented. Broadside radiation from the monopole is achieved by surrounding it with an asymmetric array of semicircular metallic strips on a grounded dielectric slab. With this implementation we demonstrate high gain with a weight of less than 80 g and lower side lobe levels compared to previous designs fed by a resonant slot. The measured antenna shows an experimental gain of 19.4 dBi with only 5 periods and a side lobe level of −16 dB (−20.3 dB for the numerical ideal case at f = 12.6 GHz), along with a narrow 6º beamwidth
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.
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.