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Publications

Publications by Diana Viegas

2014

Optical Sensing Based in Plasmonics and the Metamaterials Enhancement Factor

Authors
Moayyed, H; Leite, IT; Coelho, L; Santos, JL; Guerreiro, A; Viegas, D;

Publication
Latin America Optics and Photonics Conference

Abstract

2013

SPR Sensing with Bimetallic Layers in Optical Fibers and Phase Interrogation

Authors
Moayyed, H; Leite, IT; Coelho, L; Santos, JL; Viegas, D;

Publication
8TH IBEROAMERICAN OPTICS MEETING AND 11TH LATIN AMERICAN MEETING ON OPTICS, LASERS, AND APPLICATIONS

Abstract
An analytical model based on geometrical optics and multilayer transfer matrix method is applied to determine the sensing properties of tapered optical fiber based SPR sensors incorporating bimetallic (Gold and Silver) layers, particularly when phase interrogation is considered. Phase interrogation is studied as a methodology to attain enhanced sensitivities. The performance of the sensing heads as function of the bimetallic layers and taper parameters is analyzed. It is shown the bimetallic combination is capable to provide larger values of sensitivity compared with the single layer approach. The results derived from this study are guiding the experimental study of these structures.

2013

Ag-nanowire metamaterials: Spectral reflectance analysis and homogenization models

Authors
Leite, IT; Silva, AO; Hierro Rodriguez, A; Sousa, CT; Fernandez Garcia, MP; Teixeira, JM; Araujo, JP; Giraldi, MT; Costa, JWCA; Viegas, D; Jorge, PAS; Guerreiro, A;

Publication
8TH IBEROAMERICAN OPTICS MEETING AND 11TH LATIN AMERICAN MEETING ON OPTICS, LASERS, AND APPLICATIONS

Abstract
In this work, we address a study of the spectral reflectance of silver nanowire metamaterials in the visible and near-infrared regions. To this end, several samples were fabricated with different fill-ratios and lattice constants, and their respective optical responses characterized in terms of these parameters. We perform a direct comparison between the collected experimental data with the values predicted by different analytical homogenization models to provide a better understanding of the effective optical behavior of this kind of metamaterials.

2015

Fiber optic hydrogen sensor based on an etched Bragg grating coated with palladium

Authors
Coelho, L; de Almeida, JMMM; Santos, JL; Viegas, D;

Publication
APPLIED OPTICS

Abstract
A study of a sensor for hydrogen (H-2) detection based on fiber Bragg gratings coated with palladium (Pd) with self-temperature compensation is presented. The cladding around the gratings was reduced down to 50 mu m diameter by a chemical etching process. One of the gratings was left uncoated, and the other was coated with 150 nm of Pd. It was observed that palladium hydride has unstable behavior in environments with high humidity level. A simple solution to overcome this problem based on a Teflon tape is presented. The sensing device studied was able to respond to H-2 concentrations in the range 0%-1% v/v at room temperature and atmospheric pressure, achieving sensitivities larger than 20 pm/% v/v. Considering H-2 concentrations in nitrogen up to 1%, the performance of the sensing head was characterized for different thicknesses of Pd coating ranging from 50 to 200 nm. (C) 2015 Optical Society of America

2015

Multiplexing of Surface Plasmon Resonance Sensing Devices on Etched Single-Mode Fiber

Authors
Costa Coelho, LCC; Marques Martins de Almeida, JMMM; Moayyed, H; Santos, JL; Viegas, D;

Publication
JOURNAL OF LIGHTWAVE TECHNOLOGY

Abstract
It is proposed the multiplexing of optical fiber-based surface plasmon resonance (SPR) sensors deployed in a ladder topology, addressed in wavelength by combining each sensor with specific fiber Bragg gratings (FBGs) and considering intensity interrogation. In each branch of the fiber layout, the FBGs are located after the sensor and the peak optical power reflected by the FBGs is a function of the relative spectral position between the SPR sensor and the FBG resonances, with the former dependent on the refractive index of the surrounding medium. The concept is tested for the multiplexing of two SPR sensors fabricated in an etched region of a single-mode fiber showing intrinsic refractive index sensitivity up to 5000 nm/RIU, which translates into a sensitivity of similar to 829 dB/RIU from the interrogation approach considered. The obtained refractive index resolution is in the order of 10(-4) RIU, and the crosstalk level between the sensors was found negligible.

2016

Analysis of a Plasmonic Based Optical Fiber Optrode With Phase Interrogation

Authors
Moayyed, H; Leite, IT; Coelho, L; Santos, JL; Viegas, D;

Publication
PHOTONIC SENSORS

Abstract
Optical fiber optrodes are attractive sensing devices due to their ability to perform point measurement in remote locations. Mostly, they are oriented to biochemical sensing, quite often supported by fluorescent and spectroscopic techniques, but with the refractometric approach considered as well when the objective is of high measurement performance, particularly when the focus is on enhancing the measurand resolution. In this work, we address this subject, proposing and analyzing the characteristics of a fiber optic optrode relying on plasmonic interaction. A linearly tapered optical fiber tip is covered by a double overlay: the inner one - a silver thin film and over it a dielectric layer, with this combination allowing to achieve, at a specific wavelength range, surface plasmonic resonance (SPR) interaction sensitive to the refractive index of the surrounding medium. Typically, the interrogation of the SPR sensing structures is performed, considering spectroscopic techniques, but in principle, a far better performance can be obtained, considering the reading of the phase of the light at a specific wavelength located within the spectral plasmonic resonance. This is the approach which is studied here in the context of the proposed optical fiber optrode configuration. The analysis performed shows the combination of a silver inner layer with a dielectric titanium oxide layer with tuned thicknesses enables sensitive phase reading and allows the operation of the fiber optic optrode sensor in the third telecommunication wavelength window.

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