Miguel Hernaez

Lossy Mode Resonance Generation With Indium-Tin-Oxide-Coated Optical Fibers for Sensing Applications

Surface plasmon resonances and lossy mode resonances (LMRs) can be generated with indium tin oxide (ITO) coated optical fibers. Both phenomena are analyzed and compared. LMRs present important advantages: they do not require a specific polarization of light, it is possible to generate multiple attenuation bands in the transmission spectrum, and the sensitivity of the device to external parameters can be tuned. The key parameter is the thickness of the ITO coating. The study is supported with both theoretical and experimental results. The main purposes are sensing and generation of multiple-wavelength filters.

Design rules for lossy mode resonance based sensors

Lossy mode resonances can be obtained in the transmission spectrum of cladding removed multimode optical fiber coated with a thin-film. The sensitivity of these devices to changes in the properties of the coating or the surrounding medium can be optimized by means of the adequate parameterization of the coating refractive index, the coating thickness, and the surrounding medium refractive index. Some basic rules of design, which enable the selection of the best parameters for each specific sensing application, are indicated in this work.

Optical Fiber Humidity Sensors Using Nanostructured Coatings of SiO

In this paper, a new optical fiber humidity sensor based on superhydrophilic coating is proposed. The electrostatic self-assembly technique has been used to create a nanometric scale surface on the tip of a standard single-mode pigtail. The fabricated sensor has demonstrated a good linearity in the range from 40% to 98% of relative humidity (RH). A variation of 10 dB in reflected optical power is achieved with a response time of only 150 ms. Among other applications, this sensor is intended to be used for monitoring the human breathing, so high dynamic performances are required, specially in the higher RH ranges.

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A comparative study of lossy mode resonances generated by depositing two different materials is presented. The two materials selected are indium tin oxide (ITO) and indium oxide. The two materials present different dielectric dispersion, which leads to the generation of single-peak lossy mode resonances with the ITO coated optical fibers and dual-peak lossy mode resonances with the In2O3 coated optical fibers. The obvious advantage of a dual-peak based measurement in the sensors field is enhanced by a sensitivity increase observed in sensors based on In2O3 if compared with those based on ITO. These characteristics are analyzed both theoretically and experimentally.

Nanoparticles

In this work, it is presented the fabrication of optical fiber refractometers in the infrared region based on the deposition of indium tin oxide (ITO) coatings onto optical fibers core. ITO coatings act as the resonance supporting layer allowing the coupling of light at specific wavelengths from the waveguide to the ITO-coating/external medium region as a function of the refractive index of the external medium. The utilization of ITO coatings allows the fabrication of robust, highly reproducible and easy to implement resonance based refractometers. The results obtained showed an average sensitivity of 3125 nm/refractive index unit, which is comparable to the existing devices based either on resonance or other techniques. The fabricated devices showed fast response and no dependence with the length of the sensitive region.

Generation of lossy mode resonances by deposition of high-refractive-index coatings on uncladded multimode optical fibers

The generation of lossy mode resonances with absorbing thin-films is analyzed with electromagnetic theory. The main differences with surface plasmon resonances are presented and some rules are given towards an optimum design of sensing devices based on absorbing thin-film coated silica substrates. The material selected for the absorbing thin-film is ITO, which is adequate for supporting both surface plasmon resonances and lossy mode resonances.

ITO Coated Optical Fiber Refractometers Based on Resonances in the Infrared Region

The fabrication of optical fiber refractometers by means of the deposition of a thin indium-oxide coating onto an optical fiber core is presented. Indium-oxide permits the guided light in the fiber to be coupled from its core to its coating, creating resonances in the infrared and visible regions. These resonances vary as a function of the external mediums refractive index, enabling the fabrication of robust and highly reproducible wavelength-based optical fiber refractometers. Moreover, two differentiated resonances have been obtained from the same device within the 500to 1700-nm spectrum. The central wavelength of the resonances can be adjusted by varying the thickness of the indium-oxide coating. The sensitivity of the dual-peak resonance-based refractometers is within the same order of magnitude when the resonances are situated in the same spectral region. The refractometers that we obtained showed a sensitivity of 4068-nm/refractive index unit (RIU) in the range 1.333-1.392 RIU, comparable to existing ones based on resonances and other techniques, with the advantage of permitting the realization of dual-peak reference measurements in different regions of the spectrum.

Generation of Lossy Mode Resonances With Absorbing Thin-Films

Quantum dot nanocoatings have been deposited by means of the Layer-by-Layer technique on the inner holes of Photonic Crystal Fibers (PCFs) for the fabrication of temperature sensors. The optical properties of these sensors including absorbance, intensity emission, wavelength of the emission band, and the full width at half maximum (FWHM) have been experimentally studied for a temperature range from to .

Dual-Peak Resonance-Based Optical Fiber Refractometers

A novel configuration able to measure simultaneously relative humidity and temperature is proposed. The sensing head is based on a long-period fiber grating (LPG) coated with silica nanospheres in-line with a fiber Bragg grating. The polymeric overlay that changes its optical properties when exposed to different humidity levels is deposited onto the LPG using the electrostatic self-assembly technique (ESA), resulting into a humidity-induced shift of the resonance wavelength of the LPG. Considering the humidity range from 20% to 50% RH, a system resolution of 1.6% RH and 2.5°C was achieved. At higher humidity, from 50% to 80% RH, the corresponding resolution values were 2.4% RH and 0.4°C.

Photonic Crystal Fiber Temperature Sensor Based on Quantum Dot Nanocoatings

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.