BUSCADOR RECOLECTA

This work introduces a novel single-package optical sensing device for multiple gas sensing, which is suitable for breath analysis applications. It is fabricated on a coverslip substrate via a sputtering technique and uses a planar waveguide configuration with lateral incidence of light. It features three sequentially ordered strips of different materials, which serve to increase the multivariate nature of the response of the device to different gases. For the proof-of-concept, the selected materials are indium tin oxide (ITO), tin oxide (SnO2), and chromium oxide III (Cr2O3), while the selected gases are nitric oxide (NO), acetylene (C2H2), and ammonia (NH3). The sensing mechanism is based on the hyperbolic mode resonance (HMR) effect, with the first-order resonance obtained for each strip located in the near infrared region. The multivariate response of the resonances and the correlation with the concentration of each gas allow training a machine learning (ML) model based on a nonlinear autoregressive neural network, enabling the accurate prediction of the concentration of each gas. The obtained limit of detection for all the gases was in the order of a few parts per billion. This innovative approach coined as the multivariate optical resonances spectroscopy demonstrates the potential of HMR-based optical sensors in combination with ML techniques for ultra-sensitive multi-gas detection applications using a single device., This work was supported by the Agencia Estatal de Investigación research projects, Spain (Grant Nos. PID2019-106231RB-I00 and PDC2023-145831-I00), and by the Institute Smart Cities of the Public University of Navarra Ph.D. student grants, Spain (Grant No. 401).

The current work describes and compares the performance of hyperbolic mode resonance (HMR)-based sensors for the detection of acetone at parts per billion (ppb) concentrations using ensemble machine learning (EML) techniques. A pair of HMR based-sensors with resonances located in the visible (VIS) and mid infrared (MIR) regions were obtained in order to train a set of ensemble machine learning models. The response of the detection system formed by both devices in the VIS and MIR regions, with the help of the EML system, allowed the limit of detection (LoD) of the sensors to be reduced by an order of magnitude. It is the first time that HMR-based sensors are shown in practical applications, at the same time that their performance is improved using EML techniques. This opens new avenues for the use of this type of HMR-based sensors for the detection of other substances, in addition to improving the performance of any optoelectronic sensor using EML techniques., This work was supported by Agencia Estatal de Investigación (PID2022-137437OB-I00 and PDC2023-145831-I00), Institute Smart Cities and Public University of Navarra Ph.D. student grant, International Mobility Scholarship of the Navarra Government, and the Radboud University.

Lossy mode resonances (LMRs) have been widely employed for the development of sensors in the last years. However, the theoretical frameworks for LMRs are scarce and difficult to systematize, hampering the development of this technology. In this work, we propose a new systemic model for assessing LMRs in arbitrary waveguide configurations, based solely on modal analysis of the unperturbed waveguide and the waveguide with a thin film optimized for LMR generation. The model is first developed for a generic waveguide, and leveraged to design, for the first time, LMRs in a silicon nitride photonic wire waveguide. It is furthermore demonstrated that the model only requires a few modes to reliably describe LMRs in D-shaped fibers, reducing the computational cost of simulating them. Therefore, the suggested model is valid for both high and low contrast waveguides, and it is considered it provides new insights about LMRs, which will help in the design of new LMR-based devices and its extension to novel platforms., This work was supported by Agencia Estatal de Investigación (grant JDC2022-048216-I, project PDC2023-145831-I00, and project TED2021-130400B-I00/AEI/ https://doi.org/10.13039/501100011033/European Union NextGeneration EU/PRTR).

This letter demonstrates the fabrication of a temperature optical sensor by printing the corresponding sensitive optical waveguide directly onto a flexible flat substrate. The printed waveguide was carried out using a coaxial needle and an electrohydrodynamic (EHD) machine. The fluorescent organic compound, rhodamine B, was used for doping the core of the printed waveguide as temperature sensible dye. The optical sensitive waveguide manufactured is compact, ensuring coupling with the input and output optical fibers. The response of the printed optical sensor was evaluated to temperature variations by measurement of both, the peak intensity and the wavelength of the fluorescence spectra. The experimental characteristic and sensitivity of the sensor were obtained., This work was supported in part by the Gobierno de Navarra under Grant PC058-059 EleSpray and in part by the Agencia Estatal de Investigación under Grant PID2022-137437OB-I00 and Grant PDC2023-145831-I00.

Los sensores ópticos basados en resonancias han tenido un papel
protagónico en el desarrollo de diversas tecnologías, especialmente
aquellos basados en modos con pérdidas en los últimos quince años. Una
de sus aplicaciones con mayor auge es la detección de gases.
En esta tesis se presentan los resultados obtenidos en el desarrollo de
sensores ópticos basados en resonancias para la detección de gases. Se
aborda el estado del arte de las tecnologías de sensores basados en
resonancias, incluyendo los SPR (Surface Plasmon Resonance,
resonancia de plasmón de superficie) y LMR (Lossy Mode Resonance,
resonancia de modos con pérdidas) en la detección de gases y
compuestos volátiles orgánicos. Los esfuerzos se centran en aspectos
fundamentales como: el empleo de sustratos que permitan la fabricación
de sensores basados en resonancias LMR y HMR (Hyperbolic Mode
Resonance, resonancia de modo hiperbólico) en longitudes de onda lo
más largas posible en la región infrarroja empleando materiales como el
calcio fluorado (CaF2), y la aplicación de técnicas de inteligencia artificial
para mejorar el rendimiento de estos sensores y hacer posible la
detección de múltiples gases., Optical sensors based on resonances have played a leading role in the
development of various technologies, especially those based on lossy
modes over the past fifteen years. One of its most rapidly growing
applications is gas detection.
This thesis presents the results obtained in the development of optical
sensors based on resonances for gas detection. It addresses the state of
the art of resonance-based sensor technologies, including SPR (Surface
Plasmon Resonance) and LMR (Lossy Mode Resonance), in the
detection of gases and volatile organic compounds. Efforts focus on
fundamental aspects such as: the use of substrates that enable the
fabrication of LMR and HMR (Hyperbolic Mode Resonance) sensors at
the longest possible wavelengths in the infrared region using materials
like calcium fluoride (CaF2), and the application of artificial intelligence
techniques to enhance the performance of these sensors and enable the
detection of multiple gases., Apoyo financiero del Instituto de Smart Cities de la Universidad Pública de Navarra (Contratos Predoctorales adscritos a Grupos de Investigación de la Universidad Pública de Navarra), el Ministerio de Ciencia e Innovación (PID2019-106231RBI00, PID2022-137437OB-I00 y PDC2023-145831-I00) y beca de movilidad de estudiante del Gobierno de Navarra., Programa de Doctorado en Tecnologías de las Comunicaciones, Bioingeniería y de las Energías Renovables (RD 99/2011), Bioingeniaritzako eta Komunikazioen eta Energia Berriztagarrien Teknologietako Doktoretza Programa Ofiziala (ED 99/2011)