Open Access
Hands-on teaching with microcontrollers
(IEEE, 2021) Ruiz Zamarreño, Carlos; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Teaching electronics can be fun and motivating when you give the students the freedom to develop their own projects but of course, with a proper supervision. This work presents a case study where the teaching of microcontrollers in the third course of the MSc in Industrial Engineering, specialty in electronics, has been moved away from a strictly academic point of view towards a project-based learning (PBL) course. Here, the students are supposed to acquire a basic microcontroller knowledge in a few lecture sessions and autonomous work in order to pass rapidly to the hands-on training and activities and the following autonomously developed project. Proposed approach has enabled to increase the student engagement and motivation during the whole semester as well as improve the student average results compared to previous cases. Moreover, the satisfaction of the students and the word of mouth from student to student has permitted to increase the number of students of the specialty of electronics in the MSc in Industrial year after year. Students' outcomes and satisfaction surveys have been analysed for seven consecutive courses.
Open Access
Lossy mode resonance sensors based on tungsten oxide thin films
(IEEE, 2020) Del Villar, Ignacio; Bohórquez Navarro, Dina Luz; Caputo, Domanico; Buzzin, Alessio; Chiavaioli, Francesco; Baldini, Francesco; Ruiz Zamarreño, Carlos; Matías Maestro, Ignacio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Tungsten oxide (WO3) thin-films fabricated on glass slides have been proven to generate lossy mode resonances (LMRs) in the visible region. Obtained devices were characterized in transmission by lateral incidence of light on the edge of glass slides. Resonances at both TE and TM polarizations were analyzed for different thicknesses and in different deposition conditions. Moreover, it was successfully proved that WO3 coated glass slides present a high sensitivity to refractive index, which opens the path to the application of this structure in the domain of optical sensors.
Open Access
Gas sensor based on lossy mode resonances by means of thin graphene oxide films fabricated onto planar coverslips
(MDPI, 2023) Vitoria Pascual, Ignacio; Gallego Martínez, Elieser Ernesto; Melendi Espina, Sonia; Hernáez Sáenz de Zaitigui, Miguel; Ruiz Zamarreño, Carlos; Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The use of planar waveguides has recently shown great success in the field of optical sensors based on the Lossy Mode Resonance (LMR) phenomenon. The properties of Graphene Oxide (GO) have been widely exploited in various sectors of science and technology, with promising results for gas sensing applications. This work combines both, the LMR-based sensing technology on planar waveguides and the use of a GO thin film as a sensitive coating, to monitor ethanol, water, and acetone. Experimental results on the fabrication and performance of the sensor are presented. The obtained results showed a sensitivity of 3.1, 2.0, and 0.6 pm/ppm for ethanol, water, and acetone respectively, with a linearity factor R2 > 0.95 in all cases.
Open Access
Improving the width of lossy mode resonances (LMRs) in double-clad fibers
(IEEE, 2023) Imas González, José Javier; Del Villar, Ignacio; Zubiate Orzanco, Pablo; Ruiz Zamarreño, Carlos; Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In this work, the characteristics of lossy mode resonances (LMRs) in double-clad fibers where the refractive index (RI) of the second cladding is lower than that of the first cladding are analyzed both numerically and experimentally. In the first place, the LMRs spectra obtained with a 75 nm TiO 2 thin film are simulated, and it is observed that a thicker second cladding improves the width of the resonances, making them narrower. Then, two experimental cases (no second cladding, and second cladding with thickness of 1.13 μm) are assessed, showing a good agreement with the previous simulations. Finally, an experimental refractometric study is carried out in liquids (surrounding medium refractive index in the 1.34 - 1.40 range) for both fibers, calculating the full width at 1 dB (FW 1dB ), the sensitivity, and the figure of merit (FOM). The FW 1dB is better for the LMR obtained on the fiber with second cladding while the sensitivity is slightly greater for the fiber without second cladding. In the case of the FOM, it is higher for the double-clad fiber as the narrowing of the resonances outweighs the lower sensitivity. These results show that the performance of LMR-based optical fiber sensors can be improved by employing double-clad fibers.
Open Access
Micro sized interdigital capacitor for humidity detection based on agarose coating
(2021) Vitoria Pascual, Ignacio; Armas, Dayron; Coronel Camones, Carlos Manuel; Ozcariz Celaya, Aritz; Ruiz Zamarreño, Carlos; Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
A micro sized interdigital capacitor has been proposed for the detection of relative humidity. The photolithography technique enables the fabrication of fingers with a size of 10x500 um. A thin film of agarose functionalizes the sensor for humidity sensing, which improves its performance by 155 times, obtaining a sensitivity of 32.98 pF/%RH.
Open Access
Optical system based on multiplexed FBGs to monitor hand movements
(IEEE, 2021) Socorro Leránoz, Abián Bentor; Díaz Lucas, Silvia; Castillo, Silvia; Dreyer, Uilian José; Martelli, Cicero; Cardozo da Silva, Jean Carlos; Uzqueda Esteban, Itziar; Gómez Fernández, Marisol; Ruiz Zamarreño, Carlos; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería Eléctrica, Electrónica y de Comunicación; Estadística, Informática y Matemáticas; Gobierno de Navarra / Nafarroako Gobernua
This contribution reports the development and characterization of an optical system based on parallel Fiber Bragg Gratings (FBGs) to monitor the movements of the wrist and fingers of a hand. The system consisted of a reflective configuration made of FBGs detecting the movements of the fingers and one more located on the wrist as a reference. All FBGs were multiplexed in order to collect the basic movements of the hand. Fibers were embedded in polydimethylsiloxane for protection and to give flexibility to the optical detection setup. Measurements of strain, angle and torsion were performed during the experiments, obtaining sensitivities up to 1.29 pm/ \mu \varepsilon in strain and 64.23 pm/° in angle. Also, a study on the influence of a single sensor on the performance of the whole system was analyzed for a complete study of this proof of concept. The obtained results present a simple system that can be used to monitor the positions of the hand or for the rehabilitation of patients suffering from neuromotor or post-stroke diseases.
Open Access
Tunable sensitivity in long period fiber gratings during mode transition with low refractive index intermediate layer
(IEEE, 2022) Del Villar, Ignacio; Montoya-Cardona, Jorge; Imas González, José Javier; Reyes-Vera, Erick; Ruiz Zamarreño, Carlos; Matías Maestro, Ignacio; Cruz, José Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Double-clad fibers where the second cladding has a lower refractive index than the first cladding, prove to be ideal structures for potentiating and tuning the sensitivity in long-period fiber gratings (LPFGs) operating in mode transition. When a thin film is deposited on the optical fiber, the second cladding performs acts as a barrier that initially prevents the transition to guidance in the thin film of one of the modes guided in the first cladding. Finally, the transition to guidance occurs with a sensitivity increase, in analogy to the tunnel effect observed in semiconductors. This improvement has been demonstrated both as a function of the thin film thickness and the surrounding medium refractive index, with enhancement factors of 4 and 2, respectively. This idea reinforces the performance of LPFGs, adding a new degree of freedom to the mode transition and the dispersion turning point phenomena. Moreover, the control of the variation of the effective index of cladding modes could be applied in other structures, such as tilted-fiber gratings or evanescent wave sensors.
Open Access
Lossy mode resonance and hyperbolic mode resonance-based optical sensors by means of Y3Fe5O12 and SrTiO3 films deposition on planar substrates
(IEEE, 2025-07-02) Correa Fernández, Ángel; Gallego Martínez, Elieser Ernesto; Ruiz Zamarreño, Carlos; Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
This letter describes the fabrication of sensor devices based on lossy mode resonance (LMR) and hyperbolic mode resonance (HMR) using for the first time as generating materials of the optical resonances both, yttrium iron garnet (Y3Fe5O12) and strontium titanate (SrTiO3) with a film thickness of 739.2 and 158.7 nm for Y3Fe5O12 (YIG) and SrTiO3, respectively. First-order resonances were observed at the visible region of the electromagnetic spectrum for both materials, LMR and HMR phenomena. RF sputtering deposition was used to fabricate metal oxide thin films on coverslips in a planar waveguide configuration, the Au metallic thin films were deposited by pulsed dc sputtering in a magnetron system from Moorfield. All devices were characterized under different surrounding medium refractive index. Sensitivities achieved values of 5862 and 5865 nm/RIU (refractive index unit) for HMR versions of Y3Fe5O12 and SrTiO3r, respectively. In addition, the response of the sensors to relative humidity and different ethanol concentrations was evaluated. The best results correspond to the Y3Fe3O3-based sensor, with a sensitivity of 0.2 nm/ppm and a limit of detection (LOD) of 183 ppm for ethanol, and 64 nm/%RH for RH, with an LOD of 2.23%RH, and because its resonance does not vanish unlike SrTiO3.
Open Access
Ammonia gas optical sensor based on lossy mode resonances
(IEEE, 2023) Armas, Dayron; Zubiate Orzanco, Pablo; Ruiz Zamarreño, Carlos; Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
This letter presents the fabrication and characterization of an ammonia (NH 3) gas optical sensor based on lossy mode resonances (LMRs). A chromium (III) oxide (Cr 2 O 3) thin film deposited onto a planar waveguide was used as LMR supporting coating. The obtained LMR shows a maximum attenuation wavelength or resonance wavelength centered at 673 nm. The optical properties of the coating can be modified as a function of the presence and concentration of NH 3 in the external medium. Consequently, the refractive index of the Cr 2 O 3 thin film will change, producing a red-shift of the resonance wavelength. Obtained devices were tested for different concentrations of NH 3 as well as repetitive cycles. Concentrations as low as 10 ppbv of NH 3 were detected at room temperature. Machine learning regression models were used to mitigate the cross-sensitivity of the device under temperature and humidity fluctuations.
Open Access
Mode transition during deposition of nanoscale ITO coatings on tilted fiber Bragg gratings
(Optica Publishing Group, 2022) Imas González, José Javier; Albert, Jacques; Del Villar, Ignacio; Ozcariz Celaya, Aritz; Ruiz Zamarreño, Carlos; Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
The mode transition phenomenon is experimentally demonstrated in tilted fiber Bragg gratings (TFBG) through the deposition of an indium tin oxide (ITO) thin film employing a DC sputtering machine.