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
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.
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
Tripod-loop metasurfaces for terahertz-sensing applications: a comparison
(MDPI, 2020) Jáuregui López, Irati; Orazbayev, Bakhtiyar; Pacheco-Peña, Víctor; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
The high electric field intensity achieved on the surface of sensors based on metasurfaces (metasensors) makes them an excellent alternative for sensing applications where the volume of the sample to be identified is tiny (for instance, thin-film sensing devices). Various shapes and geometries have been proposed recently for the design of these metasensors unit-cells (meta-atoms) such as split ring resonators or hole arrays, among others. In this paper, we propose, design, and evaluate two types of tripod metasurfaces with different complexity in their geometry. An in-depth comparison of their performance is presented when using them as thin-film sensor devices. The meta-atoms of the proposed metasensors consist of a simple tripod and a hollow tripod structure. From numerical calculations, it is shown that the best geometry to perform thin-film sensing is the compact hollow tripod (due to the highest electric field on its surface) with a mean sensitivity of 3.72 × 10−5 nm−1. Different modifications are made to this structure to improve this value, such as introducing arms in the design and rotating the metallic pattern 30 degrees. The best sensitivity achieved for extremely thin film analytes (5–25 nm thick) has an average value of 1.42 × 10−4 nm, which translates into an extremely high improvement of 381% with respect to the initial hollow tripod structure. Finally, a comparison with other designs found in the literature shows that our design is at the top of the ranking, improving the overall performance by more than one order of magnitude. These results highlight the importance of using metastructures with more complex geometries so that a higher electric field intensity distribution and, therefore, designs with better performance can be obtained.
Open Access
Labyrinth absorber based on metageometries metasurface for fungi detection
(IEEE, 2020) Jáuregui López, Irati; Rodríguez Ulibarri, Pablo; Kuznetsov, Sergei A.; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In this paper a labyrinth metasurface based in the new paradigm of metageometries is designed to operate in the Terahertz (THz) band as a biosensor. First, a numerical study is carried out to study the performance of the metasurface as a refractometer when working in two different configurations: transmission and reflection. Then, its performance as a fungi detector is evaluated and a comparison with other devices is performed, showing that the sensitivity and Figure of Merit (FOM) can be enhanced by the use of these kind of devices, in comparison with the classical approach of metaatoms. Particularly, the designed structure is able to detect 5 fungi elements arbitrarily distributed on the unit cell, which is equivalent to a concentration of 0.004/μm 2 , improving the results available in the literature by a factor of more than 4.