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
Fully metallic Luneburg metalens antenna in gap waveguide technology at V-band
(IEEE, 2023) Pérez Quintana, Dayan; Bilitos, Christos; Ruiz-García, Jorge; Ederra Urzainqui, Íñigo; Teniente Vallinas, Jorge; González-Ovejero, David; Beruete Díaz, Miguel; Institute of Smart Cities - ISC
This article presents the design of a flat Luneburg metalens antenna at V-band using gap waveguide (GW) technology. The metalens consists of a parallel plate waveguide (PPW) loaded with metallic pins whose height is modulated to get an effective refractive index that follows the Luneburg equation. A Groove GW (GGW) H-plane horn is used to illuminate the metalens, such that the rays are collimated and a planar wavefront is generated in the direction of propagation. Since the structure at hand is planar, it can be efficiently integrated on flat surfaces. Moreover, the fully metallic structure is mechanically robust and presents lower losses than lenses including dielectric substrates. A prototype has been fabricated and tested, simulations and experimental results are in very good agreement. The metalens yields an input reflection coefficient (S11) below −10 dB from 45 to 70 GHz, whereas the −3 dB gain fractional bandwidth is 26.2% with respect to a center frequency of 60 GHz, with a peak of 22.5 dB at 61 GHz. These features make this design an interesting solution for millimeter-wave (MMW) applications.
Open Access
Labyrinth metasurface for biosensing applications: numerical study on the new paradigm of metageometries
(MDPI, 2019) Jáuregui López, Irati; Rodríguez Ulibarri, Pablo; Kuznetsov, Sergei A.; Quemada Mayoral, Carlos; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
The use of metasurfaces operating in the terahertz regime as biosensor devices has attracted increased interest in recent years due to their enhanced sensitivity and more accurate detection capability. Typical designs are based on the replica of relatively simple unit cells, usually called metaatoms. In a previous paper, we proposed a new paradigm for ultrasensitive thin-film sensors based on complex unit cells, called generically metageometries or labyrinth metasurfaces. Here, we extend this concept towards biosensing, evaluating the performance of the labyrinth as a fungi detector. The sensing capabilities are numerically evaluated and a comparison with previous works in this field is performed, showing that metageometries improve the performance compared to metaatoms both in sensitivity and figure of merit, by a factor of more than four. In particular, we find that it is able to detect five fungi elements scattered on the unit cell, equivalent to a concentration of only 0.004/µm2.
Open Access
Metageometries for polycyclic aromatic hydrocarbons detection at THz range in food systems
(IEEE, 2021) Jáuregui López, Irati; Insausti Barrenetxea, Kizkitza; Beriain Apesteguía, María José; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Ingeniería Eléctrica, Electrónica y de Comunicación
Polycyclic aromatic hydrocarbons, when present in food systems, have been shown to have a detrimental effect on human health, producing carcinogenic elements. So, the implementation of processes for their detection and identification is of vital importance. Nowadays, there are different methodologies for this purpose, but they consist of expensive and time-consuming processes. Due to their enhanced sensitivity and more accurate detection capability, metageometries operating in the terahertz band arise as a new methodology to identify and detect different chemical or biological substances. In this work, we propose a labyrinth metageometry able to detect different polycyclic aromatic hydrocarbons collected in European regulations as the most critical compounds with high experimental sensitivity. Our design is also capable to distinguish between different compounds at the same concentration. This work leads the way to the design of new metastructures able to improve the current detection limits, and thus obtain a new methodology, easier and less time-consuming that the actual methods.
Open Access
THz sensing with anomalous extraordinary optical transmission hole arrays
(MDPI, 2018) Jáuregui López, Irati; Rodríguez Ulibarri, Pablo; Kuznetsov, Sergei A.; Nikolaev, Nazar A.; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Subwavelength hole array (HA) metasurfaces support the so-called extraordinary optical transmission (EOT) resonance that has already been exploited for sensing. In this work, we demonstrate the superior performance of a different resonant regime of HA metasurfaces called anomalous EOT, by doing a thorough numerical and experimental study of its ability in thin-film label-free sensing applications in the terahertz (THz) band. A comprehensive analysis using both the regular and anomalous EOT resonances is done by depositing thin layers of dielectric analyte slabs of different thicknesses on the structures in different scenarios. We carry out a detailed comparison and demonstrate that the best sensing performance is achieved when the structure operates in the anomalous EOT resonance and the analyte is deposited on the non-patterned side of the metasurface, improving by a factor between 2 and 3 the results of the EOT resonance in any of the considered scenarios. This can be explained by the comparatively narrower linewidth of the anomalous EOT resonance. The results presented expand the reach of subwavelength HAs for sensing applications by considering the anomalous EOT regime that is usually overlooked in the literature.