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
Asymmetrically and symmetrically coated tapered optical fiber for sensing applications
(SPIE, 2015) Del Villar, Ignacio; Socorro Leránoz, Abián Bentor; Corres Sanz, Jesús María; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The deposition of a non-metallic thin-film in a symmetrically coated tapered optical fiber leads to the generation of resonances due to guidance of a mode in the thin-film. At certain conditions, the resonances overlap each other, which can be avoided with an asymmetric coated tapered optical fiber, which permits to obtain resonances for TM and TE polarization separately. Numerical results showing the sensitivity to coating thickness and surrounding medium refractive index are also presented for both polarizations.
Open Access
Long period fiber gratings with overlay of variable refractive index
(IEEE, 2005) Del Villar, Ignacio; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
A theoretical analysis is presented of a long-period fiber grating (LPFG) with an overlay of variable refractive index. The highest sensitivity of the resonance wavelengths to variations in the refractive index of the overlay can be optimized. There are two key points for a good design: the selection of an overlay refractive index close to that of the cladding of the LPFG and the overlay thickness. The problem is analyzed with a numerical method based on coupled-mode theory.
Open Access
Optical fiber immunosensors optimized with cladding etching and ITO nanodeposition
(IEEE, 2018) Cardona-Maya, Yamile; Del Villar, Ignacio; Socorro Leránoz, Abián Bentor; Corres Sanz, Jesús María; Botero-Cadavid, Juan F.; Institute of Smart Cities - ISC; Gobierno de Navarra / Nafarroako Gobernua
Etched optical fiber immunosensors, with and without ITO nanodeposition, have been developed. The performance of these immunosensors has been assessed implementing an immunoassay. The sensitivity of the mmnunosensor increased by a factor of 4 with the ITO nanocoating, whereas the limit of the detection in both types of devices was 0.2 mg/L of antigens in solution.
Open Access
Sensitivity enhancement by diameter reduction in low cutoff wavelength single-mode multimode singlemode (SMS) fiber sensors
(IEEE, 2017) Goñi Carnicero, Jaime; Del Villar, Ignacio; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Two different low cutoff wavelength single-mode fibers were used in single-mode multimode single-mode (SMS) configuration with the aim of designing sensors operating at short wavelengths, where optical sources and spectrometers are less expensive than in telecommunications bands. The diameter of the SMS structure was reduced with an etching process based on hydrofluoric acid immersion. The results prove that the devices can operate at wavelength ranges from 600 to 1200 nm and that multiple peaks can be obtained, each one with a different sensitivity that is proportional to the wavelength. Moreover, a fivefold increase in sensitivity to refractive index can be obtained. This high sensitivity indicates the possibility to apply this simple and cost-effective device in other applications such as biosensors or chemical sensors.
Open Access
Lossy mode resonance sensors based on lateral light incidence in nanocoated planar waveguides
(Nature Research, 2019) Fuentes Lorenzo, Omar; 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, 2018/PC021-022
The deposition of an indium oxide (In2O3) thin film on conventional planar waveguides (a coverslip and a glass slide) allows generating lossy mode resonances (LMR) by lateral incidence of light on the waveguide and by registering the optical spectrum in a spectrometer. This novel sensing system becomes an alternative to optical fibre, the substrate where LMR-based sensors have been developed so far, since it is easier to handle and more robust. An additional advantage is that cost effective waveguides, such as slides or coverslips, can be used in a platform that resembles surface plasmon resonance-based sensors in the Kretschmann configuration but without the need for a coupling prism and with the advantage of being able to generate TE and TM LMR resonances with metallic oxide or polymer thin films. The results are corroborated with simulations, which provide in-depth understanding of the phenomena involved in the sensing system. As a proof-of-concept for the optical platform, two refractometers were developed, one with low sensitivity and for a wide range of refractive indices, and the other with higher sensitivity but for a narrower refractive index range. The sensors presented here open up the path for the development of LMR-based chemical sensors, environmental sensors, biosensors, or even the generation of other optical phenomena with the deposition of multilayer structures, gratings or nanostructures, which is much easier in a planar waveguide than in an optical fibre.
Open Access
Enhancement of lossy mode resonance sensing properties by the introduction of an intermediate low-refractive-index layer
(Optica, 2023) Armas, Dayron; Kwietniewski, Norbert; Matías Maestro, Ignacio; Burnat, Dariusz; Smietana, Mateusz; Del Villar, Ignacio; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Devices based on the lossy mode resonance (LMR) effect have found numerous sensing applications. Herein, the enhancement of the sensing properties by the introduction of an intermediate layer between the substrate and the LMR-supporting film is discussed. Experimental results for a silicon oxide (SiO2) layer of tuned thickness between a glass slide substrate and a thin film of titanium oxide (TiO2) prove the possibility of significantly increasing the LMR depth and the figure of merit (FoM) for refractive index sensing applications, which is supported by a numerical analysis using the plane wave method for a one-dimensional multilayer waveguide. The application of the intermediate layer allows the introduction of a new, to the best of our knowledge, degree of freedom into the design of LMR-based sensors, resulting in improved performance for demanding fields such as chemical sensing or biosensing.
Open Access
Analysis of one-dimensional photonic band gap structures with a liquid crystal defect towards development of fiber-optic tunable wavelength filters
(Optical Society of America, 2003) Del Villar, Ignacio; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Claus, Richard O.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
A theoretical analysis of a fiber optical photonic band gap based tunable wavelength filter is presented. The design presented here is based on the quarter wave reflector with a liquid crystal defect layer in the middle of the structure. The filter generated by the structure is shifted in wavelength as the voltage applied to the structure is modified. Some critical parameters are analyzed: the effect of the consideration of fiber as the first layer and not the input medium in the shape of the filter, the number of layers of the structure, and the thickness of the defect layer. This last parameter determines the width of the wavelength sweep of the filter, but is limited by the creation of more defects. Some rules of practical implementation of this device are also given.
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
SnO2 based optical fiber refractometers
(SPIE, 2012) Sánchez Zábal, Pedro; Ruiz Zamarreño, Carlos; Hernáez Sáenz de Zaitigui, Miguel; Del Villar, Ignacio; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
In this work, the fabrication and characterization of refractometers based on lossy mode resonances (LMR) is presented. Tin dioxide (SnO2) films deposited on optical fibers are used as the LMR supporting coatings. These resonances shift to the red as a function of the external refractive index, enabling the fabrication of robust and highly reproducible wavelength-based optical fiber refractometers. The obtained SnO2-based refractometer shows an average sensitivity of 7198 nm/refractive index unit (RIU) in the range 1.333-1.420 RIU.