Open Access
Design of terahertz sensors based on metasurfaces for fungal infection detection
(2016) Jáuregui López, Irati; Beruete Díaz, Miguel; Rodríguez Ulibarri, Pablo; Escuela Técnica Superior de Ingenieros Industriales y de Telecomunicación; Telekomunikazio eta Industria Ingeniarien Goi Mailako Eskola Teknikoa
El trabajo propuesto trata sobre el diseño de sensores en la banda de terahercios para la detección de “thin films” y microorganismos, en particular de hongos. En primer lugar, se ha realizado un estudio profundo de simulación del comportamiento de varias metasuperficies para su uso como sensores de detección de invasiones fúngicas, mediante el software comercial CST Microwave Studio. Tres tipos de estructuras han sido estudiadas: en primer lugar, un “cross-dipole”, seguido de un “hole array” y, finalmente, una estructura selectiva en frecuencia, en dos configuraciones diferentes (transmisión y reflexión). Se han realizado estudios paramétricos variando la concentración de microorganismos o grosor de analito depositados sobre cada estructura. Se ha acometido la optimización de las estructuras con mejores perspectivas en la aplicación de biosensado. Una vez realizado el estudio estadístico de dichas estructuras, un estudio experimental de las más prometedoras, usando la instrumentación disponible en el TERALAB ha sido realizado. Los resultados demuestran las prometedoras perspectivas del sensado de THz basado en metasuperficies
Open Access
Terahertz and infrared sensing with metasurfaces and spectroscopy techniques
(2023) Jáuregui López, Irati; Beruete Díaz, Miguel; Insausti Barrenetxea, Kizkitza; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Los metamateriales aparecen en los primeros años del siglo XXI como materiales artificiales con parámetros inusuales, que presentan un comportamiento electromagnético exótico, con más posibilidades para el control de la radiación electromagnética. Desde su primera realización experimental, la investigación en el campo del electromagnetismo tuvo un gran impulso y, como resultado, se han propuesto numerosos diseños basados en metasuperficies (la versión plana de los metamateriales) para diversas aplicaciones como las telecomunicaciones, seguridad, espectroscopía, imagen, sensado, etc. En esta Tesis se investiga el uso de dispositivos inspirados en el paradigma de las metasuperficies para aplicaciones de sensado, operando en el régimen frecuencial de los terahercios. El contenido de la Tesis se puede dividir en tres partes diferenciadas que se relacionan con los diferentes estudios que se han llevado a cabo. En primer lugar, el diseño numérico y experimental de metasensores para el sensado de películas delgadas, muestras biológicas, y químicas. Para ello, se presentan dos tipos de estructuras basadas en metasuperficies: un diseño con una geometría complicada que permite obtener resultados con una elevada sensibilidad; y un diseño basado en matrices de agujeros que explota el fenómeno de la transmisión extraordinaria. Por otra parte, se investiga el efecto de la geometría en los patrones de los metasensores y su influencia en la calidad de la detección, mediante la modificación geométrica de un diseño basado en tripolos. Por último, se investiga la aplicación de la espectroscopía de infrarojo medio para el análisis de productos oxidativos en carne de origen animal.
Open Access
Design of THz metasurfaces for thin-film sensing
(2018) Jáuregui López, Irati; Beruete Díaz, Miguel; Escuela Técnica Superior de Ingenieros Industriales y de Telecomunicación; Telekomunikazio eta Industria Ingeniarien Goi Mailako Eskola Teknikoa
El trabajo propuesto trata sobre el diseño de metasuperficies en la banda de los terahercios para su uso como sensores de películas muy delgadas. En primer lugar, se ha llevado a cabo un estudio profundo de simulación de varias metasuperficies y de su actuación como sensores, mediante el software comercial CST Microwave Studio. Se han estudiado dos tipos de estructuras: una metasuperficie “laberinto”, con una compleja geometría, y dos “hole arrays” con distintos grosores de substrato, con el objetivo de controlar la aparición de la resonancia correspondiente a la transmisión óptica extraordinaria (EOT), y hacer una comparación entre la EOT regular y la anómala. Se ha llevado a cabo un estudio paramétrico variando el grosor de la película depositada en cada estructura. Una vez realizado el estudio estadístico, se ha procedido a realizar un estudio experimental, que muestra un buen acuerdo con los resultados de simulación. Estos resultados demuestran la excelente actuación de este tipo de estructuras en el sensado de películas delgadas, mejorando los resultados presentes en la literatura.
Open Access
Labyrinth metasurface absorber for ultra-high-sensitivity terahertz thin film sensing
(Wiley, 2018) Jáuregui López, Irati; Rodríguez Ulibarri, Pablo; Urrutia Azcona, Aitor; Kuznetsov, Sergei A.; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
In this work, a labyrinth metasurface sensor operating at the low‐frequency edge of the THz band is presented. Its intricate shape leads to a high electric field confinement on the surface of the structure, resulting in ultrasensitive performance, able to detect samples of the order of tens of nanometers at a wavelength of the order of millimeters (i.e., five orders of magnitude larger). The sensing capabilities of the labyrinth metasurface are evaluated numerically and experimentally by covering the metallic face with tin dioxide (SnO2) thin films with thicknesses ranging from 24 to 345 nm. A redshift of the resonant frequency is observed as the analyte thickness increases, until reaching a thickness of 20 μm, where the response saturates. A maximum sensitivity of more than 800 and a figure of merit near 4500 nm−1 are achieved, allowing discriminating differences in the SnO2 thickness of less than 25 nm, and improving previous works by a factor of 35. This result can open a new paradigm of ultrasensitive devices based on intricate metageometries overcoming the limitations of classical metasurface sensor designs based on periodic metaatoms.
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.
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
THz tripod metasurfaces for sensing applications: from the basic, to more elaborated designs
(IEEE, 2021) Jáuregui López, Irati; Orazbayev, Bakhtiyar; Pacheco-Peña, Víctor; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In this work, we propose, design, and evaluate three types of : three types of metasurfaces using tripod-shaped unit cells when working as thin-film sensing devices. The three meta-atoms of the proposed metasensors area simple solid tripod, a hollow tripod, and a hollow tripod structure with arms.The best design showed a mean numerical sensitivity of 1.42 × 10−4nm for extremely thin samples, meaning an improvement of 381% with respect to the initial designs. These results highlight the importance of using metastructures with complex geometries that enable high-intensity electric field distributions over the whole metasurface.
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
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
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.