Open Access
High sensitivity lossy-mode resonance refractometer using low refractive index PFA planar waveguide
(Elsevier, 2023) Domínguez Rodríguez, Ismel; Corres Sanz, Jesús María; Matías Maestro, Ignacio; Ascorbe Muruzabal, Joaquín; Del Villar, 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
In this work a new strategy to improve the sensitivity of refractometers based on lossy-mode resonances has been proved. The proximity of the PFA (tetrafluoroethylene-perfluoro polymer) substrate refractive index to that of water has permitted to implement an optical refractometer with a sensitivity of 41,034 nm per refractive index unit (nm/RIU) for refractive indices ranging from 1.3318 to 1.3347. The work is supported with both theoretical and experimental results. This high sensitivity can be used for the development of LMR based chemical sensors and biosensors, where a low limit of detection is required, with the additional advantage of a simple disposable planar configuration.
Open Access
Increasing the sensitivity of an optic level sensor with a wavelength and phase sensitive single-mode multimode single-mode (SMS) fiber structure
(IEEE, 2017) Fuentes Lorenzo, Omar; Del Villar, Ignacio; Vento Álvarez, José Raúl; Socorro Leránoz, Abián Bentor; Gallego Martínez, Elieser Ernesto; Corres Sanz, Jesús María; Matías Maestro, Ignacio; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
The sensitivity of a liquid level sensor based on a single-mode-multimode-single-mode fiber structure has been increased by hydrofluoric acid etching. The etching process was analyzed and monitored both theoretical and experimentally, which permitted to observe that a sinusoidal spectrum can be obtained for low diameters. As an example, a 2.77 fold sensitivity increase was attained by etching from diameter 125 to 50 μm. Moreover, the sinusoidal shape of the optical spectrum permitted to monitor liquid level changes both in wavelength and phase. The cross sensitivity of the sensor to refractive index and temperature was also studied.
Open Access
Fiber-optic immunosensor based on lossy mode resonances induced by indium tin oxide thin-films
(IEEE, 2017) Socorro Leránoz, Abián Bentor; Del Villar, Ignacio; Corres Sanz, Jesús María; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC
A novel immunosensor based on lossy mode resonances (LMRs) induced in optical fibers is developed in this contribution. Indium tin oxide (ITO) is sputtered on the optical substrate to generate an LMR in the transmission spectrum. Type G immunoglobulins (IgGs) are then attached to the ITO-coated fiber using (3-glycidyloxypropyl)trimethoxysilane (GPTMS). A phosphate buffer saline solution containing anti-IgGs is used to detect the biological reactions. The presented device is capable of detecting anti-IgG concentrations up to 10 nM. These results will permit the fabrication of biosensors based on a covalent attachment of bioreceptors over an LMR inducing thin-film.
Open Access
Multichannel refractometer based on lossy mode resonances
(IEEE, 2022) Fuentes Lorenzo, Omar; Corres Sanz, Jesús María; Domínguez Rodríguez, Ismel; Del Villar, Ignacio; Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In this work a new multiparameter sensor platform based on lossy mode resonances is presented. The structure consists of a soda-lime optical slab waveguide butt-coupled to multimode optical fibers. A variable thickness thin-film is deposited to generate multiple independent resonances on the same waveguide, which can be monitored using a single spectrometer. In order to show the potentiality of the structure, a broad resonance was selectively narrowed by etching sections of the LMR producer thin film. The spectral width is progressively reduced, allowing to selectively isolate independent resonances, which opens the path for multiple LMR generation in the same spectra in a multiparameter sensing platform. The experimental results were corroborated with a theoretical analysis based on the finite difference method (FDM). As a proof of concept, two refractometers on the same waveguide were fabricated and tested using PDMS cells. This platform can be easily miniaturized in order to integrate multiple sensors at low cost, what can be of interest for the development of multi-analyte biosensors probes. IEEE
Open Access
Extraordinary sensitivity with quasi-lossy mode resonance mode transition bands in long period fiber gratings
(Elsevier, 2025-01-16) González Salgueiro, Lázaro José; Del Villar, Ignacio; Corres Sanz, Jesús María; 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 study presents a novel sensor design utilizing a long-period fiber grating (LPFG) deposited with a TiO2 nanocoating via atomic layer deposition. The study combines theoretical simulations and experimental validation to optimize the grating period and modulation index to operate in the mode transition with a quasi-lossy mode resonance (LMR) behavior, i.e., the LPFG attenuation bands shift similarly to LMRs. This enables the achievement of a remarkable sensitivity of 78 nm/nm, allowing for the detection of sub-angstrom variations in film thickness, which is critical for applications in semiconductor manufacturing. Our setup facilitates continuous monitoring of the transmission spectrum, enabling real-time adjustments during deposition to maximize sensitivity. As proof of concept for the applicability of the sensor as a refractive index sensor, we demonstrated exceptional sensitivity for nitrogen detection, achieving around 10,000 nm/RIU, with a figure of merit of 200. This marks one the highest sensitivities reported for optical fiber gas sensors and suggests this technology could revolutionize the field duet to its simplicity in terms of sensor design.
Open Access
Humidity sensor based on Bragg gratings developed on the end facet of an optical fiber by sputtering of one single material
(MDPI, 2017) Ascorbe Muruzabal, Joaquín; Corres Sanz, Jesús María; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The refractive index of sputtered indium oxide nanocoatings has been altered just by changing the sputtering parameters, such as pressure. These induced changes have been exploited for the generation of a grating on the end facet of an optical fiber towards the development of wavelength-modulated optical fiber humidity sensors. A theoretical analysis has also been performed in order to study the different parameters involved in the fabrication of this optical structure and how they would affect the sensitivity of these devices. Experimental and theoretical results are in good agreement. A sensitivity of 150 pm/%RH was obtained for relative humidity changes from 20% to 60%. This kind of humidity sensors shows a maximum hysteresis of 1.3% relative humidity.
Open Access
Optimized strain long-period fiber grating (LPFG) sensors operating at the dispersion turning point
(IEEE, 2018) Del Villar, Ignacio; Fuentes Lorenzo, Omar; Chiavaioli, Francesco; Corres Sanz, Jesús María; Matías Maestro, Ignacio; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica; Gobierno de Navarra / Nafarroako Gobernua
Two phenomena for enhancing the sensitivity of longperiod fiber gratings are combined toward an increase of the sensitivity to strain of this type of devices: the dispersion turning point (DTP) and the cladding diameter reduction by an etching process. The results prove that sensitivities up to 20 pm/με can be attained, which is a ten-fold improvement compared to the previous works. The sensitivity in the grating region, which is subjected to etching, does not depend on the order of the cladding mode responsible for the attenuation bands generated in the transmission spectrum, but on the proximity to the DTP for each mode order. On the other hand, the sensitivity to strain of the global structure, including the region without etching, can be increased for lower order modes in a perceptible way if the length of the etched region is smaller compared to the fiber region under stress. The experimental results are supported with simulations based on coupled-mode theory and on FIMMWAVE, which allows understanding the phenomena involved during the sensing process.
Open Access
Metallic-dielectric layer based hyperbolic mode resonances in planar waveguides
(IEEE, 2024) González Salgueiro, Lázaro José; Del Villar, Ignacio; Corres Sanz, Jesús María; Goicoechea Fernández, Javier; 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
In this research article, we present a comprehensive investigation into the integration of dielectric and metallic layers on optical waveguides, specifically targeting sensing applications. By utilizing a single bilayer of metal and dielectric on a planar waveguide that meets the conditions of a hyperbolic metamaterial, we significantly enhance the visibility of lossy mode resonances generated with a single dielectric layer, in what can be considered as a hyperbolic mode resonance (HMR), without compromising sensitivity. This improvement leads to an enhanced figure of merit and a reduction of the signal-to-noise ratio. Real-time evolution of spectra during the dielectric layer deposition allows us to establish a map of the multiple phenomena involved, such as surface plasmon resonance, lossy mode resonance, and mode transition. Combining these phenomena in a single structure leads to an unprecedented enhancement in sensing capabilities, demonstrating the potential of dielectric-metallic layer integration on optical waveguides for advanced sensing applications. Moreover, the optimized sensing performance offers promising opportunities for on-chip sensing devices and various applications in biomedicine, environmental monitoring, and chemical analysis.
Open Access
Simultaneous generation of surface plasmon and lossy mode resonances in the same planar platform
(MDPI, 2022) Fuentes Lorenzo, Omar; Del Villar, Ignacio; Domínguez Catena, Iris; Corres Sanz, Jesús María; Matías Maestro, Ignacio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
A planar waveguide consisting of a coverslip for a microscope glass slide was deposited in one of its two faces with two materials: silver and indium tin oxide (ITO). The incidence of light by the edge of the coverslip permitted the generation of both surface plasmon and lossy mode resonances (SPRs and LMRs) in the same transmission spectrum with a single optical source and detector. This proves the ability of this optical platform to be used as a benchmark for comparing different optical phenomena generated by both metal and dielectric materials, which can be used to progress in the assessment of different sensing technologies. Here the SPR and the LMR were compared in terms of sensitivity to refractive index and figure of merit (FoM), at the same time it was demonstrated that both resonances can operate independently when silver and ITO coated regions are surrounded by different refractive index liquids. The results were supported with numerical results that confirm the experimental ones.
Open Access
Interdigital concept in photonic sensors based on an array of lossy mode resonances
(Nature Research, 2021) Domínguez Rodríguez, Ismel; Del Villar, Ignacio; Fuentes Lorenzo, Omar; Corres Sanz, Jesús María; Matías Maestro, Ignacio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Multi-parameter detection is key in the domain of sensors. Here it is demonstrated that an indium tin oxide (ITO) nanocoating can be used to generate multiple lossy mode resonances (LMRs) in the optical spectrum. To achieve this, a nanocoating with a gradient in thickness is generated on the surface of a planar waveguide, permitting broadening of the LMR because the position of an LMR in the optical spectrum is directly related to the nanocoating thickness. The nanocoating with a gradient in thickness contributes multiple LMRs, each one centred at a different wavelength. With a further etching or deposition using a mask, a pattern of deposited and non-deposited regions can be created, resulting in isolation of the LMRs by preventing LMR overlap. This enables tracking of each central wavelength separately, which can be tuned through control of the gradient or nanocoating pattern. The array of LMR-based sensors is a photonics analogue to the interdigital concept in electronics, enabling multiple resonances to be used for multiparameter sensing.