Open Access
Trends in the design of intensity-based optical fiber biosensors (2010–2020)
(MDPI, 2021) Acha Morrás, Nerea de; Socorro Leránoz, Abián Bentor; Elosúa Aguado, César; Matías Maestro, Ignacio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Gobierno de Navarra / Nafarroako Gobernua
There exists an increasing interest in monitoring low concentrations of biochemical species, as they allow the early-stage detection of illnesses or the monitoring of the environment quality. Thus, both companies and research groups are focused on the development of accurate, fast and highly sensitive biosensors. Optical fiber sensors have been widely employed for these purposes because they provide several advantages for their use in point-of-care and real-time applications. In particular, this review is focused on optical fiber biosensors based on luminescence and absorption. Apart from the key parameters that determine the performance of a sensor (limit of detection, sensibility, cross-sensibility, etc.), other features are analyzed, such as the optical fiber dimensions, the sensing set ups and the fiber functionalization. The aim of this review is to have a comprehensive insight of the different aspects that must be taken into account when working with this kind of sensors.
Open Access
Improving the width of lossy mode resonances in a reflection configuration D-shaped fiber by nanocoating laser ablation
(Optical Society of America, 2020) Fuentes Lorenzo, Omar; Vaiano, Patrizio; Del Villar, Ignacio; Corres Sanz, Jesús María; Matías Maestro, Ignacio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Gobierno de Navarra / Nafarroako Gobernua
The full width at half maximum (FWHM) of lossy mode resonances (LMRs) in the optical spectrum depends on the homogeneity of the thin film deposited. In this Letter, a method for improving the FWHM is applied for an LMR generated by a D-shaped optical fiber in reflection configuration. For this purpose, three samples with different attenuation were deposited with DC sputtering thin films of SnO2−x, and a further controlled immersion of the samples in water was performed. A laser-cleaner method was used to improve the FWHM characteristics of one of the samples from 106 to 53 nm. This improvement can be applied to thin-film-based sensors where there is a problem with the inhomogeneity of the coating thickness. Moreover, with this technique, it was proved that a coated length of just 3–4 mm permits the generation of an LMR, with implications for the miniaturization of the final device.
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
Advances in sensors using lossy mode resonances
(SPIE, 2023-11-27) Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
Lossy mode resonance (LMR) is a phenomenon that is observed in the optical spectrum when a mode that progresses through a waveguide starts to be guided in a thin film deposited on this waveguide under certain conditions, mainly related to materials and angles of incidence. An important property that LMRs have is that they can be guided into the thin film with both magnetic (TM) and electrical (TE) polarized light, unlike the other two main types of optical resonances with the same modus operandi that complete this trilogy, surface plasmon resonances (SPRs) and surface exciton plasmon resonances (SEPR). Regarding the potential materials that make up thin films, they include dielectrics suchs as metal oxides such as titanium dioxide (TiO2), zinc oxide (ZnO), tin oxide (SnO2) or polymers. In all cases it must be fulfilled that the real part of the refractive index must be greater than its imaginary part, unlike also the SPR and SEPR. As for the angles of incidence, they must be close to 90º, which explains the success of deposition of thin films around an optical fiber to obtain sensors based on LMR, although interesting results have recently been obtained using planar waveguides. This work will present the main milestones obtained during more than a decade using LMR-based sensors for the detection of multiple parameters. Among these interesting aspects, we can mention the sensitivity records achieved, hybridization with other sensing technologies or the possibility of multiplexing multiple sensors on the same substrate, just to mention a few.
Open Access
Nano-photonic crystal D-shaped fiber devices for label-free biosensing at the attomolar limit of detection
(Wiley, 2024-07-23) Del Villar, Ignacio; González-Valencia, Esteban; Kwietniewski, Norbert; Burnat, Dariusz; Armas, Dayron; Pitula, Emil; Janik, Monika; Matías Maestro, Ignacio; Giannetti, Ambra; Torres, Pedro; Chiavaioli, Francesco; Smietana, Mateusz; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Maintaining both high sensitivity and large figure of merit (FoM) is crucial in regard to the performance of optical devices, particularly when they are intended for use as biosensors with extremely low limit of detection (LoD). Here, a stack of nano-assembled layers in the form of 1D photonic crystal, deposited on D-shaped single-mode fibers, is created to meet these criteria, resulting in the generation of Bloch surface wave resonances. The increase in the contrast between high and low refractive index (RI) nano-layers, along with the reduction of losses, enables not only to achieve high sensitivity, but also a narrowed resonance bandwidth, leading to a significant enhancement in the FoM. Preliminary testing for bulk RI sensitivity is carried out, and the effect of an additional nano-layer that mimics a biological layer where binding interactions occur is also considered. Finally, the biosensing capability is assessed by detecting immunoglobulin G in serum at very low concentrations, and a record LoD of 70 aM is achieved. An optical fiber biosensor that is capable of attaining extraordinarily low LoD in the attomolar range is not only a remarkable technical outcome, but can also be envisaged as a powerful tool for early diagnosis of diseases.
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
Silver nanoparticles loaded electrospun nanofibers for humidity optical fiber sensing
(2012) Urrutia Azcona, Aitor; Rivero Fuente, Pedro J.; Goicoechea Fernández, Javier; Rodríguez, Yoany; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
In this work, a new optical device based on silver loaded electrospun nanofibers (ENFs) for measuring Relative Humidity is proposed. Fiber mats composed of poly(acrylic acid) and β-cyclodextrin were deposited onto an optical fiber core by electrospinning. Afterwards the ENFs were submitted to a thermal curing. Then, the ENFs were loaded with Ag nanoparticles (Ag NPs) synthesized using a Ag+ loading step and a further reduction step with dimethylamine borane (DMAB). Several load/reduction cycles were performed. Ag NPs enhance significantly the optical response of the polymer-only fiber mats. The Ag NPs loaded ENF sensor was tested using controlled variations of Relative Humidity (RH). The results showed a very fast response of the absorbance spectra enabling high performance applications such as human breathing monitoring.
Open Access
Spectral evolution with incremental nanocoating of long period fiber gratings
(Optical Society of America, 2006) Del Villar, Ignacio; Corres Sanz, Jesús María; Achaerandio Alvira, Miguel; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The incremental deposition of a thin overlay on the cladding of a long-period fiber grating (LPFG) induces important resonance wavelength shifts in the transmission spectrum. The phenomenon is proved theoretically with a vectorial method based on hybrid modes and coupled mode theory, and experimentally with electrostatic self-assembly monolayer process. The phenomenon is repeated periodically for specific overlay thickness values with the particularity that the shape of the resonance wavelength shift depends on the thickness of the overlay. The main applications are the design of wide optical filters and multiparameter sensing devices.
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
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.