Fiber optic multiple-wavelength filter based on one dimensional photonic bandgap structures with defects

In this paper, a theoretical analysis is given of an optical fiber multiple-wavelength tunable filter based on a onedimensional (1-D) photonic bandgap (PBG) structure with four defects. To understand the positioning of the modes in the bandgap, a previous analysis of structures with one and two defects is performed. By adequate parameterization, it will be possible to control the central wavelengths of the various filters of the device. Parameters responsible for this effect are the contrast of refractive indexes of high- and low-index layers, the optical thickness of the defects, and the number of layers stacked among the defects related to those stacked at the extremes. In addition to this, the finesse of the filters can be controlled by the adequate addition of layers among defects. As a result, a simple 1-D PBG structure with defects will permit designing almost any multiple-wavelength filter, with immediate application in the treatment of wavelength-division- multiplexed (WDM) signals. The possibility of the tunability of this device can be introduced if materials are included whose refractive index changes with some parameter, such as temperature, voltage, or strain. As an example, liquid crystals change their refractive index with an applied voltage, leading to a shift of the central wavelengths of the filters.This work was supported by Spanish Ministerio de Ciencia y Tecnologia and FEDER Research Grants CICYT-TIC 2003-00909 and CICYT-TIC 2001-0877-C02-02; Gobierno de Navarra and FPU MECD Grant

Trends in the design of wavelength-based optical fibre biosensors (2008–2018)

During the last decades, both governments and companies have been committed to the continuous checking of biological parameters, which can prevent extra costs to administrations. A very efficient way to address this issue is by designing biosensors. This contribution reviews the advances made using optical fibre technology, which have lately agglutinated much of the scientific interest related to the development of biosensors. However, the wide number of publications describing the use of optical fibre for detecting biomarkers has probably blurred the main goal: obtaining portable, simple, easy-to-handle and cost-effective biosensors. With this purpose, this contribution presents some optical fibre structures which have been analysed in terms of several optical parameters of interest from a photonics point of view: sensitivity, quality factor, full width at half minimum, limit of detection and figure of merit. This has made it possible to classify the most advanced optical fibre sensing techniques and, hence, their suitability when developing biosensing applications.This work was supported by the Regional Government of Navarra, Spain (projects with references 72/2015 and PC021-022) and by the Agencia Estatal de Investigación (Spanish National Research Agency) through the project with reference TEC2016-78047-R

Optical biosensors: a quick overview

This work aims to provide a brief overview of the latest trends in the domain of optical biosensors.We want to thank the funding from Ministerio de Ciencia, Innovación y Universidades (FPU18/03087) and Agencia Estatal de Investigación (PID2019-106231RB-I00 TEC

Energy harvesting approaches in IoT scenarios with very low ambient energy

Trabajo presentado a la International Conference on Renewable Energies and Power Quality (ICREPQ’19). Tenerife, 2019The feasibility of multi-source energy harvesting in Internet of Things (IoT) scenarios with low and intermittent ambient energy is addressed. As a relevant case study, application to a smart cargo container system is analysed. The most relevant features of the main energy sources available in this target application are identified, and various transducers adapted to such sources are evaluated. Measurement results indicate that combined piezoelectric and thermoelectric generation inside cargo containers can significantly extend the battery lifetime of IoT end nodes embedded in such containers.This work was funded by Grant TEC2016-80396-C2-1-R (AEI/FEDER) and Obra Social La Caixa - Fundación Caja Navarra (Convocatoria 2018 de Captación de Talento)

Optimization of fiber bragg gratings inscribed in thin films deposited on D-shaped optical fibers

A fiber Bragg grating patterned on a SnO2 thin film deposited on the flat surface of a D-shaped polished optical fiber is studied in this work. The fabrication parameters of this structure were optimized to achieve a trade-off among reflected power, full width half maximum (FWHM), sensitivity to the surrounding refractive index (SRI), and figure of merit (FOM). In the first place, the influence of the thin film thickness, the cladding thickness between the core and the flat surface of the D-shaped fiber (neck), and the length of the D-shaped zone over the reflected power and the FWHM were assessed. Reflected peak powers in the range from −2 dB to −10 dB can be easily achieved with FWHM below 100 pm. In the second place, the sensitivity to the SRI, the FWHM, and the FOM were analyzed for variations of the SRI in the 1.33–1.4 range, the neck, and the thin-film thickness. The best sensitivities theoretically achieved for this device are next to 40 nm/RIU, while the best FOM has a value of 114 RIU−1.This work has been supported by the Spanish Ministry of Universities through the FPU18/03087 grant (Formación de Profesorado Universitario) and the Spanish Ministry of Science and Innovation PID2019-106231RB-I00 TEC Research fund

ESA-based in-fiber nanocavity for hydrogen–peroxide detection

A fiber-optic sensor sensitive to hydrogen peroxide has been designed based on the electrostatic layer-by-layer selfassembly method. Prussian blue has been deposited in a polymeric structure formed by Poly(allylamine hydrochloride) and poly(acrylic acid). The concentration that can be detected range between 10 6–10 3 M, and recovery of the sensor after immersion into a reductive agent was demonstrated. The response of the sensor is independent of thepHfor values that range between 4–7.4. Some rules for estimation of the refractive index of the material deposited and the thickness of the bilayers are also presentedThis work was supported by Spanish CICYT Research Grants TIC 2003-00909 and TIC 2001-0877-C02- 02; Gobierno de Navarra and FPU MECD grant

Wavelength and intensity based lossy mode resonance breathing sensor

Copper oxide (CuO) allows the generation of lossy mode resonance (LMR) in a wide wavelength range of the optical spectrum, both in the visible and the near-infrared (NIR). For this, it is necessary to use a configuration based on the lateral incidence of light on the edge of a planar waveguide structure. On the other hand, the use of additional coatings of tin oxide (SnO2) and agarose allows an increase in the sensitivity of the sensor, in response to the breathing monitoring. The sensors were characterized, both in intensity and wavelength. In both cases their behavior depends on the position of the LMR in the optical spectrum. Therefore, it is convenient to extract the design rules that allow an optimal behavior of the sensor. In this sense, sensors located in the NIR presented a better behavior in terms of sensitivity and quality of the signal. In addition, the devices were tested in different conditions: repetitive tests at different distances, oral and nasal breathing, and breathing after doing physical exercise.The authors would to acknowledge the partial support to the Agencia Estatal de Investigacion (AEI) from the Spanish Ministry of Economy and Competitiveness (PID2019-106231RB-I00 and PID2019-106070RB-I00 research funds) and the predoctoral research grant of the Public University of Navarra

Nanofabrication of phase-shifted Bragg gratings on the end facet of multimode fiber towards development of optical filters and sensors

This work describes the process of nanofabrication of phase-shifted Bragg gratings on the end facet of a multimode optical fiber with a pulsed DC sputtering system based on a single target. Several structures have been explored as a function of parameters such as the number of layers or the phase-shift. The experimental results, corroborated with simulations based on plane-wave propagation in a stack of homogeneous layers, indicate that the phase-shift can be controlled with a high degree of accuracy. The device could be used both in communications, as a filter, or in the sensors domain. As an example of application, a humidity sensor with wavelength shifts of 12 nm in the range of 30 to 90% relative humidity (200 pm/% relative humidity) is presented.This work was supported by the Spanish Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) (TEC2016-78047-R)

Improving the width of lossy mode resonances in a reflection configuration D-shaped fiber by nanocoating laser ablation

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.Gobierno de Navarra, Ayuda a Movilidad Internacional 2019; Agencia Estatal de Investigación (TEC2016-79367-C2-2-R.)

Simultaneous generation of surface plasmon and lossy mode resonances in the same planar platform

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.The authors would like to acknowledge the partial support to the Agencia Estatal de Investigacion (AEI) PID2019-106070RB-I00 and PID2019-106231RB-I00 research funds, and the predoctoral research grants of the Public University of Navarra