BUSCADOR RECOLECTA

A fiber optic liquid-level sensor based on a long period grating (LPG) is proposed and experimentally validated. The principle of operation is based on a technique used to analyze microwave photonics filters. A 4-cm-long LPG cascaded with a high-reflectivity fiber Bragg grating is employed to achieve a continuous liquid-level sensor. The measurements have been performed using a modulator and a photo-detector with a modest bandwidth of less than 500 MHz, showing a sensitivity of −12.71 dB/cm and a standard deviation of 0.52 dB. One of the significant advantages of such sensing structure is that it is based on low-bandwidth radio frequency and off-the-shelf photonic components. In addition, the simple proposed scheme presents good repeatable performance and proves to be intrinsically robust against environmental changes, stable, and easy to reconfigure., This work was supported in part by the Accion Financiada por el Ministerio de Educacion, Cultura y Deporte through the framework of the Programa de Campus de Excelencia Internacional VLC/Campus, in part by the Spanish MINECO under Project TEC2014-60378-C2-1-R, in part by the Grant of the SANTIAGO GRISOLIA Program, in part by the Research Excellency Award Program GVA PROMETEO 2013/012, in part by the Project TEC2013-43679-R, and in part by an UPNA Predoctoral Grant. The associate editor coordinating the review of this paper and approving it for publication was Dr. Anna G. Mignani.

A humidity and temperature optical fiber sensor based on a long-period grating (LPG), which can provide simultaneous response to both magnitudes, is proposed and demonstrated via experiments. Previously, the LPG was fully coated with humidity sensitive nanostructured polymeric thin films by the Layer-by-Layer (LbL) nano assembly technique. Hence the surrounding refractive index was changed, so provoking wavelength shifts of the attenuation bands of the transmission spectrum. This fully coated LPG was exposed to relative humidity (RH) and temperature tests, varying from 20% to 80% RH and from 25 to 85ºC, respectively. Then, half of the LPG coating was chemically removed and this results in the splitting of the main attenuation band into two different contributions. When this semi-coated LPG was also exposed to RH and temperature tests, the new two attenuation bands presented different behaviors for humidity and temperature. This novel dual-wavelength based sensing method enables the simultaneous measurement of RH and temperature using only one LPG., This work was supported in part by the Spanish Ministry of Economy and Competitiveness - through the projects CICYT-FEDER TEC2013-43679-R and TEC2014-60378-C2-1-R. It was also supported by a UPNA pre-doctoral research grant, by the Program of International Excellence Campus VLC/Campus, by the grant of program SANTIAGO GRISOLIA, and by the Research Excellency Award Program GVA PROMETEO 2013/012.

Two simple optical fibre structures that do not require the inscription of a grating, a cladding removed multimode optical fibre
(CRMOF) and a single-mode multimode single-mode structure (SMS), are compared in terms of their adequateness for sensing
once they are coated with thin-films.The thin-film deposited (TiO2/PSS) permits increasing the sensitivity to surrounding medium
refractive index. The results obtained can be extrapolated to other fields such as biological or chemical sensing just by replacing the
thin-film by a specific material., This work was supported in part by the Spanish Ministry of
Education and Science-FEDER TEC2013-43679-R.

Due to the risks that water contamination implies for human health and environmental protection, monitoring the quality of water is a major concern of the present era. Therefore, in recent years several efforts have been dedicated to the development of fast, sensitive, and selective sensors for the detection of heavy metal ions. In particular, fluorescent sensors have gained in popularity due to their interesting features, such as high specificity, sensitivity, and reversibility. Thus, this review is devoted to the recent advances in fluorescent sensors for the monitoring of these contaminants, and special focus is placed on those devices based on fluorescent aptasensors, quantum dots, and organic dyes., This work was supported by the Spanish State Research Agency (AEI) and the Spanish Ministry of Economy and Competitiveness through the TEC2016-79367-C2-2-R project. Nerea de Acha would also like to acknowledge her pre-doctoral fellowship (reference BES-2014-069692) funded by the Spanish Ministry of Economy and Competitiveness through the TEC2013-43679-R project.

The fabrication and characterization of optical fiber biosensor based on Lossy Mode Resonances (LMR) to detect C-reactive protein (CRP) are presented. Indium tin oxide (ITO) coatings deposited on side-polished D-shaped optical fibers are used as LMR supporting coatings. The aptamer was immobilized on the ITO film using the Layer-by-Layer (LbL) nano-assembly process. The optical fiber sensor presented shows a high selectivity and low limit detection., This work was supported by a Pre-Doctoral Research Grant of the Public University of Navarra, Spanish Economy and Competitiveness Ministry-Feder TEC2013-43679-R and Fundación CAN2015-70221 Research Grants.

A reflection configuration setup for long-period
fiber gratings is presented. It permits to obtain a unique band
with attenuation double than that obtained in transmission
configuration, which is interesting for applications where this
value is reduced (e.g., the mode transition phenomenon). The
method is based on the deposition of a silver mirror at the
end of the optical fiber, which permits to absorb the power
transmitted through cladding modes and to avoid the generation
of interferometric bands. The method also solves the requirement
of a precise cleave or to polish the end of the grating, a drawback
present in other publications. The versatility of the setup has been
proved by application of the cladding etching technique until
the attenuation band corresponding with the first guided mode
in the cladding is visualized in an optical spectrum analyzer.
The experimental results are supported by the numerical data
obtained with a method based on the exact calculation of core
and cladding modes and the utilization of coupled mode theory, This work was supported in part by
the Spanish Ministry of Education and Science-FEDER TEC2013-43679-R and
TEC2013-46643-C2-1-R.

A humidity and temperature optical fiber sensor based on a long-period grating (LPG), which can provide simultaneous response to both magnitudes, is proposed and demonstrated via experiments. Previously, the LPG was fully coated with humidity sensitive nanostructured polymeric thin films by the Layer-by-Layer (LbL) nano assembly technique. Hence the surrounding refractive index was changed, so provoking wavelength shifts of the attenuation bands of the transmission spectrum. This fully coated LPG was exposed to relative humidity (RH) and temperature tests, varying from 20% to 80% RH and from 25 to 85 °C, respectively. Then, half of the LPG coating was chemically removed and this results in the splitting of the main attenuation band into two different contributions. When this semi-coated LPG was also exposed to RH and temperature tests, the new two attenuation bands presented different behaviors for humidity and temperature. This novel dual-wavelength based sensing method enables the simultaneous measurement of RH and temperature using only one LPG., This work was supported in part by the Spanish Ministry of Economy and Competitiveness – through the projects CICYT-FEDER TEC2013-43679-R and TEC2014-60378-C2-1-R. It was also supported by a UPNA pre-doctoral research grant, by the Program of International Excellence Campus VLC/Campus, by the grant of program SANTIAGO GRISOLÍA, and by the Research Excellency Award Program GVA PROMETEO 2013/012.

Here we show an optical refractometer with a giant sensitivity of 304,360 nm per refractive index unit(nm/RIU). This sensitivity corresponds to a resolution of 3.28 × 10−9RIU if a standard optical spectrumanalyzer with a resolution of 1 pm is used. This record sensitivity is obtained by means of a lossy moderesonance (LMR) optical fiber sensor in a surrounding media with refractive index around 1.45. Thisachievement implies that the utilization of the LMR phenomenon opens the door to devices and systemsthat can beat, in terms of sensitivity, those used currently in real-time biomolecular analysis such assurface plasmon resonance (SPR) devices., This work was supported in part by the Spanish Ministry of
Economy and Competitiveness (MINECO)-under contract FEDER TEC2013-43679-R

In this paper, a new sensor system for relative humidity measurements based on a SnO2 sputtering deposition on a microstructured optical fiber (MOF) low-finesse Fabry-Pérot (FP) sensing head is presented and characterized. The interrogation of the sensing head is carried out by monitoring the Fast Fourier Transform phase variations of the FP interference frequency. This method is low-sensitive to signal amplitude variations and also avoids the necessity of tracking the evolution of peaks and valleys in the spectrum. The sensor is operated within a wide humidity range (20%-90% relative humidity) with a maximum sensitivity achieved of 0.14rad/%. The measurement method uses a commercial optical interrogator as the only active element, this compact solution allows real time analysis of the data., We also thank the Spanish Government projects TEC 2013-47264-C2-2-R, TEC2013-43679-R Innocampus and the INTERREG SUDOE Project SOE3/P2/P714 as well as to the FEDER Funds.

A sputtering process has been applied to deposit quarter-wavelength stacks on the end facet of cleaved optical fibers by using only one sputtering target. Standard multimode optical fibers were used as substrates to fabricate broadband filters, and the experimentally measured spectral responses of these devices are shown. Periodical changes in the refractive index of the coating have been achieved by changing the vacuum chamber pressure. A reflected peak with a full-width at half-maximum of 20 nm centered at 440 nm has been obtained, which provides a good structure for the development of optical fiber sensors working with the wavelength detection technique. This optical structure can be used for several purposes: as tunable wavelength filters or optical fiber sensors or to improve the performance of fluorescence sensors. A theoretical analysis of these structures corroborates the experimental results and allows some rules to be obtained., This work was supported by a
Public University of Navarra PhD Grant and by the Spanish Economy and
Competitiveness Ministry, TEC-2013-43679-R.

Luminescence-based sensing applications range from agriculture to biology, including
medicine and environmental care, which indicates the importance of this technique as a detection tool.
Luminescent optical sensors are required to be highly stable, sensitive, and selective, three crucial
features that can be achieved by fabricating them by means of the layer-by-layer nano-assembly
technique. This method permits us to tailor the sensors0 properties at the nanometer scale, avoiding
luminophore aggregation and, hence, self-quenching, promoting the diffusion of the target analytes,
and building a barrier against the undesired molecules. These characteristics give rise to the
fabrication of custom-made sensors for each particular application., This work was supported by the Spanish State Research Agency (AEI) through the TEC2016-
79367-C2-2-R project and the European Regional Development Fund (ERDF-FEDER). Nerea de Acha would also
like to acknowledge her pre-doctoral fellowship (reference BES-2014-069692) funded by the Spanish Ministry of
Economy and Competitiveness through the TEC2013-43679-R project.

In this work a high sensitivity optical fiber humidity sensor (OFHS) is presented. The configuration chosen for this purpose is a cladding-etched single mode optical fiber (CE-SMF) coated with a thin film of tin oxide (SnO2). The etching has been made using hydrofluoric acid (HF) and the coating has been fabricated by means of sputtering. Tin oxide was used to build the nano-coating which produces the Lossy Mode Resonance (LMR) and works as sensitive material. Theoretical and experimental results are shown and compared. The device was tested using a climatic chamber in order to obtain the response of the OFHS to relative humidity. Changes greater than 130 nm have been obtained for relative humidity varying from 20% to 90%, which gives a sensitivity of 1.9 nm/%RH., This work was supported by a Public University of Navarra PhD
Grant and by the Spanish Economy and Competitiveness Ministry
TEC-2013-43679-R Research Grant.

Desde la primera publicación relacionada con las fibras micro estructuradas (MOFs), el desarrollo de sensores basados en fibra óptica (OFSs), que utilizan este tipo de fibras, se ha visto incrementado atrayendo el interés de numerosos grupos de investigación debido al importante papel que juegan en numerosas aplicaciones. Debido a sus propiedades y estructuras únicas, las MOFs son muy útiles en aplicaciones ópticas de
sensado, especialmente de gases y compuestos orgánicos volátiles (VOCs). Por estas razones, esta tesis doctoral propone la utilización de este tipo de fibras para generar y desarrollar nuevas estructuras y montajes, capaces de detectar estos parámetros, gases y VOCs. Además, se han realizado diferentes estudios y se han utilizado diferentes técnicas (destacando la transformada rápida de Fourier (FFT) y la multiplexación WDM…), para mejorar las características de los sensores, intentando conseguir de esta manera que el sistema final fuera lo más competitivo posible., Since the first publications related to Microstructured Optical Fibres (MOFs), the development of Optical Fibre Sensors (OFSs), based on this type of fibres, has been increased attracting the interest of many research
groups because of the important role that they play in diverse applications. Due to their unique geometric structures and features, MOFs are very useful for optical sensing applications, especially gases and Volatile Organic Compounds (VOC) sensing. Taking it into account, this PhD. work proposes the utilization of MOFs to carry out and to develop new structures and set-ups capable to detect these parameters, gases and VOCs. Moreover, different studies and techniques, such as Fast Fourier Transform (FFT) or WDM multiplexing, have been used with the aim of improving the features of the sensors trying to make the final system as competitive as possible., La realización de este trabajo ha sido posible gracias a las aportaciones económicas recibidas por parte de la Universidad Pública de Navarra (UPNA), así como del patrocinio de la UPNA y del Ministerio de Economía y Competitividad, a través de los proyectos CICYT fondos TEC2013-43679-R, TEC2016-79367-C2-2-R. Este trabajo fue posible también gracias a los proyectos concedidos por el Gobierno de Navarra, con referencia 2016/PI012 EXCELSEN y a la financiación otorgada por la Fundación CAN a través de los proyectos CAN2015-70221 y BINACS: Bio Inspired Nanocoatings for Cellular Scaffolds., 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 (ED 99/2011)

Integrated optical devices comprised of multiple material systems are able to achieve unique performance characteristics, enabling applications in sensing and in telecommunications. Due to ease of fabrication, the majority of previous work has focused on polymer-dielectric or polymer-semiconductor systems. However, the environmental stability of polymers is limited. In the present work, a hybrid device comprised of an indium tin oxide (ITO) coating on a silicon dioxide toroidal resonant cavity is fabricated. Finite element method simulations of the optical field in the multi-material device are performed, and the optical mode profile is significantly altered by the high index film. The quality factor is also measured and is material loss limited. Additionally, its performance as a temperature sensor is characterized. Due to the high thermo-optic coefficient of ITO and the localization of the optical field in the ITO layer, the hybrid temperature sensor demonstrates a nearly 3-fold improvement in performance over the conventional silica device., This work has been supported by institutions both in Spain and in the USA.
A pre-doctoral research grant of the Public University of Navarra and the Spanish Ministry
of Economy and Competitiveness FEDER TEC2013-43679-R project from Spain. Also, the
National Institute of Health through the Director’s New Innovator Award Program
[1DP2OD007391-01] from the United States of America.

A fiber optic liquid-level sensor based on a long period grating (LPG) is proposed and experimentally validated. The principle of operation is based on a technique used to analyze microwave photonics filters. A 4-cm-long LPG cascaded with a high-reflectivity fiber Bragg grating is employed to achieve a continuous liquid-level sensor. The measurements have been performed using a modulator and a photo-detector with a modest bandwidth of less than 500 MHz, showing a sensitivity of -12.71 dB/cm and a standard deviation of 0.52 dB. One of the significant advantages of such sensing structure is that it is based on low-bandwidth radio frequency and off-the-shelf photonic components. In addition, the simple proposed scheme presents good repeatable performance and proves to be intrinsically robust against environmental changes, stable, and easy to reconfigure., This work was supported in part by the Acción Financiada por el Ministerio de Educación, Cultura y Deporte through the framework of the Programa de Campus de Excelencia Internacional VLC/Campus, in part by the Spanish MINECO under Project TEC2014-60378-C2-1-R, in part by the Grant of the SANTIAGO GRISOLÍA Program, in part by the Research Excellency Award Program GVA PROMETEO 2013/012, in part by the Project TEC2013-43679-R, and in part by an UPNA Predoctoral Grant.

This work presents a refractive index sensor based on a long period fiber grating
(LPFG) made in a reduced cladding fiber whose low order cladding modes have the turning
point at large wavelengths. The combination of these parameters results in an improved
sensitivity of 8734 nm/refractive index unit (RIU) for the LP0,3 mode in the 1400-1650
wavelength range. This value is similar to that obtained with thin-film coated LPFGs, which
permits to avoid the coating deposition step. The numerical simulations are in agreement with
the experimental results., This work was supported in part by the Spanish Ministry of Education and Science-FEDER
TEC2013-43679-R. J.L. Cruz also acknowledges financial support of project TEC2013-46643-C2-1-R, and the Generalitat Valenciana project PROMETEOII/2014/072.

A lo largo de esta tesis se presenta el estudio y diseño de varias plataformas de guía-ondas ópticas, con el fin de ver su viabilidad a la hora de usarlas como biosensores sobre fibra óptica u otros sustratos fotónicos. En este trabajo se depositan estructuras ópticas como una fibra monomodo desnuda, un estrechamiento en fibra óptica o una fusión de fibras mono – multi – monomodo (SMS) con películas delgadas de materiales usando técnicas nanotecnológicas como el ensamblado capa a capa (LbL-assembly) o el sputtering. Además, se dedica un capítulo al estudio de microresonadores toroidales depositados por rotación (spin-coating). El objetivo es generar o mejorar las prestaciones en resolución y sensibilidad de los fenómenos resonantes que se pueden obtener en estas estructuras ópticas, para luego detectar reacciones biológicas que den lugar a un futuro diagnóstico precoz de enfermedades., Along this thesis, the study and design of several optical waveguide platforms is presented, in order to check their viability when used as biosensors based on either optical fiber or other photonic substrates. In this work, some fiber-optic-based structures such as cladding removed multimode structures, tapered single-mode fibers and single-mode – multimode – single-mode fibers are deposited with thin-films of materials, using nanotechnology-based methods such as layer-by-layer assembly (LbL-assembly) or sputtering. Moreover, a brief chapter is focused on the study of toroidal microring resonators deposited by spin-coating. The final objective is to generate or enhance the parameters of the resonant phenomena obtained in these structures, in terms of resolution and sensitivity. Then, a biological detection is addressed and characterized, to see if they are able to perform a future early diagnosis for illnesses., La realización de este trabajo ha sido posible gracias a las aportaciones económicas recibidas por parte de la Universidad Pública de Navarra (UPNA), así como del patrocinio de la UPNA y del Ministerio de Economía y Competitividad, a través de los proyectos CICYT fondos FEDER TEC2010-17805, TEC2013-43679-R e IPT-2011-1212-920000 (PMEL)., Programa Oficial de Doctorado en Ingeniería y Arquitectura (RD 1393/2007), Ingeniaritzako eta Arkitekturako Doktoretza Programa Ofiziala (ED 1393/2007)

Novel protein sensors based on tapered optical fibres modified with Au coatings deposited using two different procedures
are proposed. Au-based coatings are deposited onto a nonadiabatic tapered optical fibre using (i) a novel facile method
composed of layer-by-layer deposition consisting of polycation (poly(allylamine hydrochloride), PAH) and negatively charged SiO2
nanoparticles (NPs) followed by the deposition of the charged Au NPs and (ii) the sputtering technique. The Au NPs and Au thin
film surfaces are then modified with biotin in order to bind streptavidin (SV) molecules and detect them. The sensing principle is
based on the sensitivity of the transmission spectrum of the device to changes in the refractive index of the coatings induced by the
SV binding to the biotin. Both sensors showed high sensitivity to SV, with the lowest measured concentration levels below 2.5 nM.
The calculated binding constant for the biotin-SV pair was 2.2 × 10−11 M−1 when a tapered fibre modified with the LbL method was
used, with a limit of detection (LoD) of 271 pM. The sensor formed using sputtering had a binding constant of 1.01 × 10−10 M−1
with a LoD of 806 pM. These new structures and their simple fabrication technique could be used to develop other biosensors., This work was supported in part by the Spanish Ministry
of Economy and Competitiveness-CICYT-FEDER TEC2013-43679R Research Grant and UPNA predoctoral and mobility
research grants. The authors also acknowledge the support
of UK Engineering and Physical Sciences Research Council
Platform grant (EP/H02252X/1) and responsive mode grant
(EP/L010437/1). The authors would like also to acknowledge
the support of the EPSRC EP/G061661/1 Advanced Ultrasonics
Platform Grant, University of Nottingham, Dean of
Engineering Faculty Award.

Silicon wafers coated with IndiumTinOxide (ITO) by application of sputtering technique have been
characterized after different post-annealing techniques, showing that this last factor is critical for the
quality of the thin-film and for the creation and tuning of both surface plasmon resonances and lossy
mode resonances. By adequate selection of the ITO thin-film thickness both resonances can be tracked in
the same spectrum, which can be used in sensor and optical communications fields., This work was supported in part by the Spanish Ministry of
Education and Science-FEDER TEC2013-43679-R.

This work presents the development of high sensitive, selective, fast and reusable C-reactive protein (CRP) aptasensors. This novel approach takes advantage of the utilization of high sensitive
refractometers based on Lossy Mode Resonances generated by thin indium tin oxide (ITO) films fabricated onto the planar region of D-shaped optical fibers. CRP selectivity is obtained by means of the
adhesion of a CRP specific aptamer chain onto the ITO film using the Layer-by-Layer (LbL) nano-assembly fabrication process. The sensing mechanism relies on resonance wavelength shifts originated by
refractive index variations of the aptamer chain in presence of the target molecule. Fabricated devices show high selectivity to CRP when compared with other target molecules, such as urea or creatinine,
while maintaining a low detection limit (0.0625 mg/L) and fast response time (61 s). Additionally, these sensors show a repetitive response for several days and are reusable after a cleaning process in
ultrapure water., This work was supported by a Pre-Doctoral Research Grant of
the Public University of Navarra, Spanish Economy and Competitiveness Ministry-Feder TEC2013-43679-R and Fundación
CAN2015-70221 Research Grants.

Tin doped indium oxide (ITO) coatings fabricated onto D-shaped
optical fibers are presented as the supporting medium for Lossy Mode
Resonances (LMRs) generation. The characteristic geometry of ITO-coated
D-shaped optical fibers enables to observe experimentally LMRs obtained
with both TM and TE polarized light (LMRTM and LMRTE). This permits to
obtain a maximum transmission decay of 36 dB with a LMR spectral width
of 6.9 nm, improving that obtained in previous works, where the LMRs
were a combination of an LMRTM and an LMRTE. Surrounding medium
refractive index (SMRI) sensitivity characterization of LMRTM has been
performed obtaining a maximum sensitivity of 8742 nm/RIU in the range
1.365-1.38 refractive index units (RIU) which overcomes that of surface
plasmon resonance-based optical fiber devices presented in recent works., This work was supported by the Spanish Economy and Competitiveness Ministry-Feder TEC2013-43679-R Research Grant.

Optical fiber sensors are of great interest due to their intrinsic advantages over electronic sensors. In this work, the
sensing characteristics of two different and novel optical fiber devices are compared, after simultaneously depositing a
thin-film using the layer-by-layer assembly deposition process. The first one is an SMS structure, formed by splicing two
single-mode fiber pigtails on both sides of a coreless multimode fiber segment. This structure induces an interferometric
phenomenon that generates several attenuation and transmission bands along the spectrum. These bands are sensitive to
variations in the surrounding refractive index, although this sensitivity has been enhanced by a TiO2/PSS thin-film. The
other device is a 40 mm uncladded segment of a 200 µm-core multimode optical fiber. When coated by a TiO2/PSS thinfilm, part of the light transmitted into the uncladded core is coupled into the thin-film, generating a lossy mode resonance
(LMR). The absorption peaks due to these phenomena red-shift as long as the thin-film thickness increases or the
external RI becomes higher. The performance of these devices as refractometers and relative humidity sensors are tested.
Results show that the LMR-based sensor is more sensitive in both situations, in spite of its lower sensitivity. Particularly,
it presents a 7-fold sensitivity enhancement when measuring surrounding medium refractive index changes and a 10-fold
sensitivity enhancement when measuring environmental relative humidity. To our knowledge, this is the first time that a
comparative study between SMS and LMR sensors is performed., This work was supported by the Spanish Economy and Competitiveness Ministry project FEDER TEC2013-43679-R and by a Public University of Navarra pre-doctoral research grant.

Nanoparticles are very interesting because of their surface properties, different from bulk materials. Such properties
make possible to endow ordinary products with new functionalities. Their relatively low cost with respect to other
nano-additives make them a promising choice for industrial mass-production systems. Nanoparticles of different
kind of materials such as silver, titania, and zinc oxide have been used in the functionalization of fibers and fabrics
achieving significantly improved products with new macroscopic properties. This article reviews the most relevant
approaches for incorporating such nanoparticles into synthetic fibers used traditionally in the textile industry allowing to
give a solution to traditional problems for textiles such as the microorganism growth onto fibers, flammability, robustness
against ultraviolet radiation, and many others. In addition, the incorporation of such nanoparticles into special ultrathin
fibers is also analyzed. In this field, electrospinning is a very promising technique that allows the fabrication of ultrathin
fiber mats with an extraordinary control of their structure and properties, being an ideal alternative for applications such
as wound healing or even functional membranes., This work was supported in part by the Spanish Ministry of Economy and
Competitiveness—CICYT-FEDER TEC2013-43679-R research grant, and an
UPNA pre-doctoral research grant.

The use of nanoparticles (NPs) in scientific applications has attracted the attention of many researchers in the last few years. The use of NPs can help researchers to tune the physical characteristics of the sensing coating (thickness, roughness, specific area, refractive index, etc.) leading to enhanced sensors with response time or sensitivity better than traditional sensing coatings. Additionally, NPs also offer other special properties that depend on their nanometric size, and this is also a source of new sensing applications. This review focuses on the current status of research in the use of NPs within coatings in optical fiber sensing. Most used sensing principles in fiber optics are briefly described and classified into several groups: absorbance-based sensors, interferometric sensors, fluorescence-based sensors, fiber grating sensors, and resonance-based sensors, among others. For each sensor group, specific examples of the utilization of NP-embedded coatings in their sensing structure are reported., This work was supported in part by the Spanish Ministry of Economy and Competitiveness CICYT-FEDER TEC2013-43679-R Research Grant and a UPNA predoctoral research grant.

In this work, we present a study about the generation and analysis of optical resonances caused by gold
nanorods (GNRs) embedded in films. GNRs were embedded in polymeric thin films using the Layerby-Layer nanoassembly (LbL) deposition technique. Polymer/GNRs thin films of different thicknesses
were deposited on the surface of cladding removed optical fibers for sensing. The spectral responses of
the optical fiber sensors were monitored during the build-up of the thin films. The generation of two
Localized Surface Plasmon Resonances (LSPRs) associated to the GNRs was observed in thinner coatings.
These devices with around 12 polymer/GNRs bilayers were characterized as refractometers, providing
an intensity-based sensitivity up to 75.69 dB/RIU. For thicker polymer/GNRs overlays, both LSPRs bands
were also generated and, additionally, it was observed a new Lossy Mode Resonance (LMR) band due
to modes coupled to the sensitive coating. The dependence of these three resonance bands with the
surrounding refractive index was studied. Finally, these sensors were tested in a climatic chamber in the
20-90% relative humidity (RH) range and the LMR showed a good sensitivity to RH changes while the
LSPR bands remained very stable in comparison. Results showed an excellent sensitivity of 11.2 nm/%RH
for the LMR, confirming the potential of this type of optical fiber sensor based on the combination of
LSPRs and LMRs bands., This work was supported in part by the Spanish Ministry of Economy and Competitiveness - CICYT-FEDER TEC2013-43679R, TEC2016-79367-C2-2-R, TEC2016-78047-R and TRA2013-48603-C4-1-R Research Grants, and a UPNA post-doctoral research grant.

A method is proposed to determine lifetime of luminescent emissions based on the phase shift measurement employing the digitalized Lissajous representation: this diagram has been typically used with analogical algorithms, whereas the proposed method is performed in digital domain, showing an improved accuracy and repeatability. The procedure is studied and tested with two different oxygen sensors that show different sensitivities and signal levels in order to confirm the no influence of the signals intensity on the calibration process.The computational cost of the proposed method is low, which makes it possible to monitor in real time luminescence sensors based on reversible quenching with a potential low cost system based on a digital signal processor (DSP)., This work was supported in part by the Spanish Ministry of
Economy and Competitiveness FEDER TEC2013-43679-R.

The mode transition and the dispersion turning point have been
explored for optimization of thin-film coated long period fiber gratings
during the last years. In this work and additional parameter, the cladding
diameter, is combined with the other two phenomena for improving the
sensitivity to the surrounding medium refractive index. The numerical data
obtained were calculated with a method based on the exact calculation of
core and cladding modes and the utilization of coupled mode theory. A
sensitivity 143 × 103 nm/RIU is obtained, the highest reported so far with
long period fiber gratings., This work was supported in part by the Spanish Ministry of Education and Science-FEDER
TEC2013-43679-R.

Lossy mode resonances (LMRs) and surface plasmon resonaces
(SPRs) are obtained experimentally with a Kretschmann
configuration using a BK7 glass prism with all sides polished
and coated with indium tin oxide (ITO). The properties
of ITO allow for obtaining LMRs and SPRs with the same
experimental setup. The results are corroborated with a
numerical method for calculation of the reflection in the
Kretschmann configuration., This work was supported in part by the Spanish
Ministry of Education and Science under contracts FEDER TEC2013-43679-R, CSD2008-00066 and TEC2011-28664-C02. The FTIR spectrometer was financed by the Spanish Ministry of Economy and
Competitiveness in the frame of the project CEI10-2-2005. M. Beruete
acknowledges funding by the Spanish Government under the research
contract program Ramón y Cajal RYC-2011-08221.

Alojado según Res. CNEAI 5/12/23, In this paper, an optical fiber interferometric humidity sensor is presented. The device consists of 1 cmlong segment of photonic crystal fiber (PCF) spliced to standard single mode fibers (SMFs), forming an
interferometer: the two collapsed interfaces between PCF and SMF segments produce the excitation and
recombination of core and cladding modes. The latter interact with a poly(allylamine hydrochloride)
(PAH) and poly(acrylic acid) (PAA) polymeric nanocoating deposited on the PCF by the well-established
layer-by-layer nano assembly (LbL) technique. Humidity modifies the index of the polymeric nanolayer
which in turns alters the cladding modes along the PCF segment and causes a detectable shift to the
interference pattern. A study of different nanocoting thicknesses is presented in order to obtain the best
possible sensibility for the sensor. Furthermore, the interrogation of the humidity sensor is presented
not only by the conventional study of the spectrum shift amplitude, but also making use of the Fast
Fourier Transform (FFT), which yields a linearization of the device response. The sensor here presented
is reproducible, can resolve 0.074% of relative humidity (RH) and operates in the 20–95% RH range.
Moreover, it exhibits response time of 0.3 s, a negligible cross sensitivity to temperature as well as long
term stability., This work was supported by the Spanish Economy and Competitivity Ministry-FEDER TEC2013-43679-R.

In this paper, a high sensitivity optical fiber pH sensor based on lossy mode resonance (LMR) generated
with transversal electric (TE) and transversal magnetic (TM) polarized light is presented. Poly(allylamine
hydrochloride) (PAH)/poly(acrylic acid) (PAA) polymeric thin-films fabricated onto side-polished Dshaped optical fibers are used as pH-sensitive as well as LMR supporting coatings. The adequate selection
of the pH-sensitive coating fabrication parameters enables to obtain devices working at different pH
regions. Two devices have been obtained in order to measure pH from 4.0 to 5.0 and from 7.0 to 8.0
respectively. Obtained optical fiber pH sensors based on TE and TM LMRs showed a maximum sensitivity
of 69 nm/pH, which means a resolution of ∼0.0008 pH units by using a conventional communications
Optical Spectrum Analyzer (OSA) with 0.06 nm resolution., This work was supported by the Spanish Economy and
Competitiveness Ministry-Feder TEC2013-43679-R and Fundación
CAN2015-70221 Research Grants

El desarrollo de nuevos materiales y métodos de deposición a escala nanométrica ha supuesto una auténtica revolución en muchas disciplinas de la investigación. En particular, en el campo de los sensores de fibra óptica, los recubrimientos nanoestructurados permiten generar efectos ópticos que no son apreciables mediante la utilización de materiales convencionales. El principal objetivo de esta tesis es la fabricación de nuevos sensores de humedad de fibra óptica basados en nanofibras y películas nanoestructuradas que posean propiedades antibacterianas para aplicaciones que operan en entornos de alta humedad y probacterianos. Para ello, el estudio y síntesis de nanopartículas de plata, y su posterior inclusión en los procesos de fabricación de recubrimientos como electrospinning y Layer-by-Layer han sido analizados para la fabricación de películas antibacterianas sobre fibra óptica. De esta forma, se han estudiado y desarrollado en este trabajo diferentes arquitecturas sensoras basadas en campo evanescente, resonancias basadas en plasmones superficiales localizados y modos de pérdidas, y fibras tipo Long period gratings., The development of novel materials and deposition methods on the nanometric scale has meant an important breakthrough in diverse fields. More specifically, in the field of optical fiber sensors, nanostructured coatings allow the generation of optical effects which are not appreciable with the utilization of thick films. This thesis aims to contribute to the development of optical fiber humidity sensors based on nanostructured coatings with antibacterial properties for pro-bacterial and high humidity environments. With this goal, the synthesis of silver nanoparticles and their posterior incorporation in the sensing coatings by means of techniques such as deposition methods as electrospinning and Layer-by-Layer assembly have been analyzed and studied for the fabrication of antibacterial nanocoatings onto optical fibers. Different sensing setups based on evanescent field, lossy mode resonances, localized surface plasmon resonances, and Long-Period gratings have been researched along this work to fulfill the development of such sensors., La realización de este trabajo ha sido posible gracias a la obtención de una beca predoctoral de la Universidad Pública de Navarra (UPNA), a las ayudas de movilidad de la UPNA, y a las aportaciones económicas recibidas por parte del Gobierno de Navarra mediante sus programas de apoyo a la investigación, además de la colaboración de la Comisión Interministerial de Ciencia y Tecnología a través de la financiación de los proyectos CICYT fondos FEDER TEC2010-17805, TEC2013-43679-R., Programa Oficial de Doctorado en Tecnologías de las Comunicaciones (RD 1393/2007), Komunikazioen Teknologietako Doktoretza Programa Ofiziala (ED 1393/2007)

El desarrollo de los sensores en fibra óptica combinado con el avance de la nanotecnología ha proporcionado una excelente oportunidad para el desarrollo de nuevas plataformas sensoras ópticas portátiles, ligeras y de alto rendimiento capaces de realizar detección in situ y en tiempo real. Esta tesis quiere contribuir al avance de la tecnología de los sensores ópticos basados en resonancias de modos con pérdidas (LMRs, por sus siglas en inglés), mejorando el rendimiento de dichos dispositivos, para luego detectar biomarcadores específicos que permitan un diagnóstico selectivo y precoz de diferentes enfermedades. En este trabajo, los LMRs generados en una fibra de tipo D permiten medir los cambios en el índice de refracción externo con una sensibilidad muy alta. En consecuencia, es posible detectar concentraciones muy bajas de analito en muestras de suero. Los resultados mostrados en esta tesis revelan el potencial de los sensores basados en LMRs para desempeñar un papel fundamental en el ámbito biomédico., The development of optical fiber sensors combined with the utilization of nanotechnologies have provided an excellent opportunity for developing portable, lightweight and high-performance optical sensing platforms for in-situ and real time detection. This thesis aims to contribute to the evolution of optic sensors based on Lossy Mode Resonances (LMRs). By improving the performance of these devices it is possible to detect specific biomarkers associated to different diseases, allowing a first diagnosis at a very early stage. The generation of Lossy Mode Resonances by means of D-shaped optical fibers makes it possible to measure surrounding refractive index changes with very high sensitivity. Consequently, it is possible to detect very low analyte concentrations in serum samples. The results shown in this thesis reveals in a tangible way the potential of optical sensors based on LMR to play a fundamental role in the biomedical field., The development of this work has been possible thanks to the economic efforts made by the Public University of Navarra (UPNA) and by the sponsoring of the Spanish Ministry of Economy and Competitiveness, through the investment in the following projects: CYCIT FEDER TEC2013-43679-R and TEC2016-78047-R. This work also supported by the Goverment of Navarre through the Project with reference PC023-024 BIOPTSENS, by the health department of the Government of Navarra with reference 64/2015 and by Fundación CAN trough the project CAN2015-70221., 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 (ED 99/2011)

Over the last decades, luminescence quenching has been established as a widespread technique for gaseous oxygen monitoring in a broad range of applications. Thus, considerable effort has been made to manufacture luminescent oxygen sensors. The performances of such sensors are determined by the oxygen indicator and the matrix that entraps this indicator as well. In spite of its versatility for fine-tuning the final features of nanostructures, the Layer-by-Layer nano-assembly technique has been rarely studied for fabricating these sensors. This could be explained by the fact that most of the optically stable and highly sensitive oxygen indicators are not water soluble. The main objective of this work is to combine these detection and deposition techniques with optical fiber setups, for the fabrication and characterization of luminescent optical fiber oxygen sensors fabricated by Layer-by-Layer nano-assembly., This PhD thesis has been possible thanks to the pre-doctoral fellowship (reference BES-2014-069692) funded by the Spanish Ministry of Economy and Competitiveness through the TEC2013-43679-R project. This work has also been supported by the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERDF-FEDER) through the TEC2016-79367-C2-2-R project and by the Government of Navarra Research Grants through the project Excelsen., 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 (ED 99/2011)

In this work, optical fiber refractometers based on the successive incorporation of gold nanoparticles have been fabricated by means of the Layer-by-Layer Embedding (LbL-E) deposition technique. This enables the apparition of two different optical phenomena, Localized Surface Plasmon Resonance (LSPR) and Lossy Mode Resonance (LMR). The absorption peaks related to both phenomena were captured during the fabrication process, showing a different evolution as a function of the resultant thickness coating. Initially, LSPR band is observed for thinner coatings, whereas multi-LMR bands are observed as the thickness coating is increased. In addition, the response of both phenomena to variations of the surrounding medium refractive index (SMRI) was monitored, studying their different sensitivities. LSPR band only shows intensity variation with negligible wavelength displacement whereas LMR bands present a strong wavelength response. The combination of both resonances opens the door in the design of self-referenced optical devices for sensing applications., This work was supported by the Spanish Economy and Competitiveness Ministry-Feder TEC2013-43679-R and by the Government of Navarra research grants.

Nanocoated D-shaped optical fibers have been proven as effective sensors. Here,
we show that the full width at half minimum (FWHM) of lossy mode resonance can be
reduced by optimizing the nanocoating width, thickness and refractive index. As a
counterpart, several resonances are observed in the optical spectrum for specific conditions.
These resonances are caused by multiple modes guided in the nanocoating. By optimizing the
width of the coating and the imaginary part of its refractive index, it is possible to isolate one
of these resonances, which allows one to reduce the full width at half minimum of the device
and, hence, to increase the figure of merit. Moreover, it is even possible to avoid the need of a
polarizer by designing a device where the resonance bands for TE and TM polarization are
centered at the same wavelength. This is interesting for the development of optical filters and
sensors with a high figure of merit., Spanish Ministry of Education and Science-FEDER (TEC2013-43679-R, TEC2016-78047-
R); Government of Navarra Health Department (64/2015, 72/2015); Government of Navarra
2016/PI008.

The fabrication and characterization of an optical fiber refractometer based on Lossy Mode Resonances (LMR) is presented. TiO2/ poly (sodium 4-styrenesulfonate) (PSS) coatings deposited on side-polished D-shaped optical fibers are used as LMR supporting coatings. LMRs are sensitive to the external medium refractive index and D-shaped optical fibers enable the observation of TE and TM LMR polarizations. These refractometers based on TE and TM LMR showed an average sensitivity of 2737 nm/RIU and 2893 nm/RIU respectively for a surrounding medium refractive index (SMRI) range from 1.35 to 1.41. This work also explores the utilization of previously described refractometers in the context of two common industrial applications such as the determination of the sugar content or °Brix in beverages and the salt concentration in sea water., This work was supported by the Spanish Economy and Competitiveness Ministry-Feder TEC2013-43679-R Research Grant.

Graphene and its derivatives have become the most explored materials since Novoselov and Geim (Nobel Prize winners for Physics in 2010) achieved its isolation in 2004. The exceptional properties of graphene have attracted the attention of the scientific community from different research fields, generating high impact not only in scientific journals, but also in general-interest newspapers. Optical fibre sensing is one of the many fields that can benefit from the use of these new materials, combining the amazing morphological, chemical, optical and electrical features of graphene with the advantages that optical fibre offers over other sensing strategies. In this document, a review of the current state of the art for optical fibre sensors based on graphene materials is presented., This work was supported in part by the following Research Grants: Spanish Economy and Competitiveness Ministry-Feder TEC2013-43679-R, Government of Navarra Health Department 64/2015, and European Commission H2020-MSCA-IF-2015 703185.

The following article appeared in Torres, V., Beruete, M., Del Villar, I., & Sánchez, P. (2016). Indium tin oxide refractometer in the visible and near infrared via lossy mode and surface plasmon resonances with Kretschmann configuration. Applied Physics Letters, 108(4), doi:10.1063/1.4941077, and may be found at http://dx.doi.org/10.1063/1.4941077., An indium tin oxide (ITO) refractometer based on the generation of lossy mode resonances (LMRs) and surface plasmon resonances (SPRs) is presented. Both LMRs and SPRs are excited, in a single setup, under grazing angle incidence with Kretschmann configuration in an ITO thin- film deposited on a glass slide. The sensing capabilities of the device are demonstrated using several solutions of glycerin and water with refractive indices ranging from 1.33 to 1.47. LMRs are excited in the visible range, from 617 nm to 682 nm under TE polarization and from 533nm to 637nm under TM polarization, with a maximum sensitivity of 700 nm/RIU and 1200 nm/RIU, respectively. For the SPRs, a sensing range between 1375 nm and 2494 nm with a maximum sensitivity of 8300 nm/RIU is measured under TM polarization. Experimental results are supported with numerical simulations based on a modification of the plane-wave method for a one- dimensional multilayer waveguide., This work was supported in part by the Spanish Ministry of Education and Science-under Contracts FEDER TEC2013-43679-R and TEC2014-51902-C2-2-R. The FTIR spectrometer was financed by the Spanish Ministry of Economy and Competitiveness in the frame of the Project CEI10-2-2005. M. Beruete acknowledges funding by the Spanish Government under the Research Contract Program Ramón y Cajal RYC-2011-08221.