Open Access
Planar-waveguide-lmr-based sensors: engineering the depth of characteristic curves
(IEEE, 2023) Shrivastav, Anand M.; Del Villar, Ignacio; Ascorbe Muruzabal, Joaquín; Corres Sanz, Jesús María; Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Lossy mode resonance (LMR)-based sensors have been proven as one of the exponentially growing research fields since the last decade. These sensors have demonstrated their capabilities in the detection of several physical, chemical, and biological entities, such as refractive index, humidity, gases, enzymes, etc. Conventionally, LMR-based sensors are developed using optical fiber as the sensing platform, but to increase the broad range of applications and better tenability, planar waveguide substrates for LMR realization have been introduced in the last few years. This provides a greater degree of freedom for the sensor design such as tunability in substrate thickness, material, and better surface immobilization. The current study focuses on evaluating the effect of substrate thickness on LMR-based optical sensors to achieve higher sensing performance. For experiments, 150-μm-thick glass coverslips are used as the thin planer substrate, which is then coated with a few nanometers thick LMR-supported SnO 2 layer using the dc sputtering method. Furthermore, to monitor the effect of the changing substrate thickness, the width of the glass coverslip is reduced through the chemical etching process using the 40% HF solution, and simultaneously, the changes in LMR spectra are analyzed. The study shows that the depth of LMR curves strongly depend on the thickness of the waveguide providing LMRs with lower substrate thickness possesses higher depth. Greater depth in LMR curves is a crucial factor in identifying the minimum transmission wavelength of resonance, making it easier to track and detect the targeted parameter. This characteristic greatly enhances the applicability of LMR-based sensors in industrial applications.
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
Ultrahigh refractive index sensitivity with lossy mode resonance in a side-polished low-index polymer optical fiber
(IEEE, 2024) López Vargas, Juan David; Matías Maestro, Ignacio; Werneck, Marcelo M.; Allil, Regina C.; Del Villar, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
This work presents a theoretical–experimental study of a refractive index (RI) sensor based on lossy mode resonances (LMRs) generated with a side-polished low-index polymer optical fiber. The theoretical part involves conducting simulations to determine the optimal coating thickness for achieving the first (1st) and second (2nd) LMR, as well as to determine their respective sensitivities. In the experimental part, a cyclic transparent fluoropolymer optical fiber is used, which is first polished and then coated with tin oxide (SnO2) thin film to obtain the LMR. The simulated and experimental results exhibit a high level of agreement. In the visible light spectrum region, the sensitivities for the first LMR are, respectively, 11 300 nm/RI unit (RIU) and 15 973 nm/RIU within the RI range of 1.333–1.345. Similarly, for the second LMR, the sensitivities are, respectively, 520 and 467 nm/RIU within the same RI range. Furthermore, experiments conducted in the near-infrared light spectrum region show a record sensitivity of 57 200 nm/RIU, while the second LMR exhibits a sensitivity of over 5 000 nm/RIU within the RI range of 1.340–1.345. These results underscore the potential of utilizing cyclic transparent optical polymer (CYTOP) fiber in various applications requiring the detection in liquid samples, such as biosensors or chemical sensors.
Open Access
Short single strand DNA detection by means of Lossy Mode Resonance based fiber-optic sensor
(IEEE, 2019-01-14) Zubiate Orzanco, Pablo; Ciáurriz Gortari, Paula; Tellechea Malda, Edurne; Santano Rivero, Desiree; Del Villar, Ignacio; Urrutia Azcona, Aitor; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ruiz Zamarreño, Carlos; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA26
Development of DNA and RNA biosensors and the associated diagnostic tests have gained growing interest in recent years. In particular, short RNA chains (around 25 oligonucleotides), known as micro RNAs, can be associated different stroke and neurodegenerative diseases. Here, we present the utilization of highly sensitive fiber optic sensor based on Lossy Mode Resonance (LMR) for the detection of single strand complementary DNA (ssDNA) associated to Huntington disease (Hsa-miR-34b).
Open Access
Optical fiber thermo-refractometer
(Optica, 2022) Imas González, José Javier; Ruiz Zamarreño, Carlos; Del Villar, Ignacio; Cardozo da Silva, Jean Carlos; Oliveira, V.; Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
This work presents the implementation of a thermo-refractometer, which integrates the measurement of both refractive index and temperature in a single optical fiber structure. To this purpose, a lossy mode resonance (LMR)-based refractometer is obtained by means of the deposition of a titanium dioxide (TiO2) thin film onto a side-polished (D-shaped) single mode fiber. Measurement and subsequent temperature compensation are achieved by means of a fiber Bragg grating (FBG) inscribed in the core of the D-shaped region. The LMR wavelength shift is monitored in transmission while the FBG (FBG peak at 1533 nm) displacement is observed in reflection. The LMR is sensitive to both the surrounding refractive index (SRI), with a sensitivity of 3725.2 nm/RIU in the 1.3324-1.3479 range, and the temperature (- 0.186 nm/°C); while the FBG is only affected by the temperature (32.6 pm/°C in the 25°C - 45°C range). With these values, it is possible to recover the SRI and temperature variations from the wavelength shifts of the LMR and the FBG, constituting a thermo-refractometer, where it is suppressed the effect of the temperature over the refractometer operation, which could cause errors in the fourth or even third decimal of the measured SRI value.
Open Access
Resonance-based optical gas sensors
(IEEE, 2025-07-02) 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
Gas sensors play a critical role in numerous human activities. Their necessity continues to grow across diverse fields as technological advancements drive demand for precision agriculture and bioengineering among other applications. Among existing sensor technologies, optical gas sensors stand out due to their ability to operate remotely in high-risk environments while remaining unaffected by electromagnetic interference. Resonance-based optical sensors offer targeted gas detection through the functionalization of their sensitive surfaces. This work focuses on reviewing the state of the art in resonance-based optical gas sensors (ROGSs), addressing their fundamental principles, recent advances in fabrication processes, waveguide designs, and materials employed both for resonance generation and as sensitive coatings. In addition, the review examines achieved sensitivity, emerging applications, and key developments in the field, including those efforts on improving ROGS performances by means of artificial intelligence techniques. The study encompasses optical sensors leveraging surface plasmon resonance, lossy mode resonance, and hyperbolic mode resonance¿the latter representing a notable breakthrough in recent years as a particular case of Bloch surface waves.
Open Access
Experimental demonstration of lossy mode resonance generation for transverse-magnetic and transverse-electric polarizations
(Optica Publishing Group, 2013) Ruiz Zamarreño, Carlos; Zubiate Orzanco, Pablo; Sagüés García, Mikel; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
This Letter, presents the fabrication of lossy mode resonance (LMR) devices based on titanium dioxide (TiO2)/ poly(sodium 4-styrenesulfonate) (PSS) coatings deposited on side-polished D-shaped optical fibers. TiO2 thin films have been obtained by means of the layer-by-layer (LbL) self-assembly technique. LbL enables us to produce smooth and homogeneous coatings on the polished side of the fiber. This permits us to couple light from the waveguide to the TiO2-coating/external medium region at specific wavelength ranges. The generation of LMRs depends on the coating thickness, so that thicker coatings can produce more resonances. LMRs are sensitive to the external medium refractive index, which allows its utilization as refractometers. The characteristic D-shaped architecture of the devices employed in this Letter enables us to distinguish TE and TM polarizations, which had not been possible before with regular optical fibers due to their cylindrical symmetry. The results presented here show for the first time the experimental demonstration of the generation of LMRs produced by both TM and TE polarizations. More specifically, for these TiO2/PSS thin films, the TM and TM modes of the LMRs show a wavelength shift of 226 nm for the first-order LMR and 56 nm for the second-order LMR.
Open Access
A comprehensive study of optical resonances in metals, dielectrics, and excitonic materials in double interface structures
(Elsevier, 2025-02-01) Imas González, José Javier; Matías Maestro, Ignacio; Del Villar, Ignacio; Ozcariz Celaya, Aritz; Vitoria Pascual, Ignacio; Ruiz Zamarreño, Carlos; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
From an optical perspective, depending on the relationship between the real (n) and imaginary (k) parts of its refractive index, three broad categories of materials can be distinguished: metals (k ¿ n), dielectrics (n ¿ k), and materials in which n ¿ k (termed here excitonic materials). The modes and optical resonances that appear in a thin film bounded by two dielectrics with similar refractive index, what we call here a double interface structure, have been widely studied in the case of metals, but not for dielectrics, or materials with n ¿ k. In this work, we propose a new approach, based on employing the phase matching condition to correlate the resonances that appear in the wavelength versus incident angle color maps of the reflected power with the modal analysis of the cross section of the structure. This analysis is performed, using an attenuated total reflection (ATR) setup, for thin film materials that belong to each of the mentioned categories: a metal (gold, Au), a dielectric (titanium dioxide, TiO2), and a material with n ¿ k (chromium, Cr). The theoretical analysis is supported with experimental results. It is demonstrated that this method enables to identify any resonance at any wavelength or incident angle, being valid for all three types of materials. Therefore, it is considered the suggested approach will help the research in these materials and in the double interface structure in the optics and photonics field.
Open Access
Rheumatoid arthritis miRNA biomarker detection by means of LMR based fiber-optic biosensor
(IEEE, 2020) Imas González, José Javier; Ruiz Zamarreño, Carlos; Zubiate Orzanco, Pablo; Campión, J.; Sánchez-Martín, L.; 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, PJUPNA26
Development of miRNA optical biosensors for disease diagnosis and monitoring has acquired relevance in recent years, due to the clinical importance of miRNA and the inherent advantages of optical sensors. Here, we present the utilization of a fiber optic sensor based on Lossy Mode Resonance (LMR) for the detection of miRNA hsa-miR-223, a promising biomarker for the diagnosis of rheumatoid arthritis (RA).
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.