Carlos R. Zamarreño

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.

Optical fiber refractometers based on lossy mode resonances supported by TiO 2 coatings

We obtain lossy mode resonances by the coupling of light from a multimode optical waveguide to a TiO(2)/PSS coating deposited with the layer-by-layer method. The resonances can be generated in a wide wavelength range from the ultraviolet to the infrared region of the optical spectrum. The transmission spectrum is monitored as a function of the number of bilayers deposited, and the experimental results agree with the theoretical predictions. Moreover, each of the resonances owns a particular sensitivity to the external refractive index. This permits us to use the sensor as a refractometer with multiple-wavelength monitorization.

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.

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

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.

An antibacterial coating based on a polymer/sol-gel hybrid matrix loaded with silver nanoparticles

In this work a novel antibacterial surface composed of an organic-inorganic hybrid matrix of tetraorthosilicate and a polyelectrolyte is presented. A precursor solution of tetraethoxysilane (TEOS) and poly(acrylic acid sodium salt) (PAA) was prepared and subsequently thin films were fabricated by the dip-coating technique using glass slides as substrates. This hybrid matrix coating is further loaded with silver nanoparticles using an in situ synthesis route. The morphology and composition of the coatings have been studied using UV-VIS spectroscopy and atomic force microscopy (AFM). Energy dispersive X-ray (EDX) was also used to confirm the presence of the resulting silver nanoparticles within the thin films. Finally the coatings have been tested in bacterial cultures of genus Lactobacillus plantarum to observe their antibacterial properties. It has been experimentally demonstrated that these silver loaded organic-inorganic hybrid films have a very good antimicrobial behavior against this type of bacteria.

Generation of Lossy Mode Resonances With Absorbing Thin-Films

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.

Dual-Peak Resonance-Based Optical Fiber Refractometers

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.

High sensitive refractometers based on lossy mode resonances (LMRs) supported by ITO coated D-shaped optical fibers.

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 (LMR(TM) and LMR(TE)). 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 LMR(TM) and an LMR(TE). Surrounding medium refractive index (SMRI) sensitivity characterization of LMR(TM) 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.

Optical fibre sensors using graphene-based materials: a review

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.

Resonances in coated long period fiber gratings and cladding removed multimode optical fibers: a comparative study

Two optical fiber devices have been coated in parallel: a long period fiber grating (LPFG) and a cladding-removed multimode optical fiber (CRMOF). The progressive coating of the LPFG by means of the layer-by-layer electrostatic-self-assembly, permits to observe a resonance wavelength shift of the attenuation bands in the transmission spectrum. The cause of this wavelength shift is the reorganization of the cladding mode effective indices. The cause of this modal reorganization can be understood with the results observed in the CRMOF coated in parallel. A lossy-mode-resonance (LMR) is generated in the same wavelength range of the LPFG attenuation bands analyzed. Moreover, the thickness range where the wavelength shift of the LPFG attenuation bands occurs coincides exactly with the thickness range where the LMR can be visualized in the transmission spectrum. These phenomena are analyzed theoretically and corroborated experimentally. The advantages and disadvantages of both optical fiber devices are explained.