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Publications

Publications by Paulo Vicente Marques

2010

Fabrication of dual analyte luminescent optrodes by photopolymerization

Authors
Jorge, PAS; Maule, C; Soppera, O; Marques, PVS;

Publication
FOURTH EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS

Abstract
A technique for the fabrication of luminescence based fiber optic optrodes with multiple analyte sensitivity is proposed. Combination of photosensitive polymers doped with different luminescent indicators was used to produce fiber probes, by self-guiding photopolymerization, having different geometries and sensing capabilities. Results demonstrating the method flexibility are shown with luminescent probes doped with CdSe/ZnS quantum dots and an organometalic ruthenium complex for simultaneous detection of oxygen and temperature.

2009

Design and Fabrication of Slotted Multimode Interference Devices for Chemical and Biological Sensing

Authors
Mayeh, M; Viegas, J; Srinivasan, P; Marques, P; Santos, JL; Johnson, EG; Farahi, F;

Publication
J. Sensors

Abstract
We present optical sensors based on slotted multimode interference waveguides. The sensor can be tuned to highest sensitivity in the refractive index ranges necessary to detect protein-based molecules or other water-soluble chemical or biological materials. The material of choice is low-loss silicon oxynitride (SiON) which is highly stable to the reactivity with biological agents and processing chemicals. Sensors made with this technology are suited to high volume manufacturing. Copyright © 2009 M. Mayeh et al.

2006

Investigation of formation mechanisms of arc-induced long-period fiber gratings

Authors
Rego, G; Ivanov, OV; Marques, PVS; Santos, JL;

Publication
Optics InfoBase Conference Papers

Abstract
By measuring intensity distributions of cladding modes and using an optimization technique we show that the perturbation which forms arc-induced gratings in standard fibers is antisymmetric, while the perturbation in boron-germanium codoped fibers is symmetric. © 2006 Optical Society of America.

2005

Chirped Bragg grating fabricated in fused fibre taper for strain-temperature discrimination

Authors
Frazao, O; Melo, M; Marques, PVS; Santos, JL;

Publication
MEASUREMENT SCIENCE & TECHNOLOGY

Abstract
In this work, two sensing heads based on the fibre Bragg gratings written in fused biconical fibre taper for simultaneous measurement of temperature and strain are proposed. In the first configuration a comparison between a uniform Bragg grating and a grating written on a tapered fibre section, resulting in a chirp grating, is evaluated. The second sensing head consists of two gratings written in two different regions of the taper section. This fibre taper has a different geometry in each conical section, achieved by stretching the fibre at different velocities during the fabrication process. These two configurations are based on the different strain and similar temperature sensitivities of the Bragg gratings used to discriminate the two physical parameters. The performances are assessed and compared. The second structure presents good performance and more sensitivity, compared to the first sensing head.

2009

Fabry-Perot refractometer based on an end-of-fiber polymer tip

Authors
Frazao, O; Caldas, P; Santos, JL; Marques, PVS; Turck, C; Lougnot, DJ; Soppera, O;

Publication
OPTICS LETTERS

Abstract
A micrometric Fabry-Perot refractometer based on an end-of-fiber polymer tip is proposed. The fiber tip, with a length of 36 mu m, was fabricated by self-guiding photopolymerization. The two-wave interferometric operation was achieved by combining the light waves generated at the interface between the single-mode fiber and the polymer tip, and at the fiber tip end (Fresnel reflection). The Fabry-Perot interferometer is coherence addressed and heterodyne interrogated, resulting into a liquid refractive index resolution of approximate to 7.5 x 10(-4). (C) 2009 Optical Society of America

2012

Temperature and Strain Sensing With Femtosecond Laser Written Bragg Gratings in Defect and Nondefect Suspended-Silica-Core Fibers

Authors
Fernandes, LA; Becker, M; Frazao, O; Schuster, K; Kobelke, J; Rothhardt, M; Bartelt, H; Santos, JL; Marques, PVS;

Publication
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
The spectral behavior in the C-band of fiber Bragg gratings (FBGs) was analyzed as a function of temperature and strain. The FBGs were fabricated in pure silica four-leaf-clover- shaped suspended-core fibers by (DUV) femtosecond laser exposure (3.6 W at 800 nm, 130 fs, 1 kHz frequency tripled to 350 fs, 650 mW at 267 nm). A defect fiber (with a hollow hole in the core) and nondefect fiber were compared both yielding approximate to 1 pm/mu epsilon sensitivity to strain but different sensitivity to temperature (from 3.0 pm/degrees C to 8.4 pm/degrees C for the defect fiber and 10 pm/degrees C for the nondefect fiber). The 16% to 70% relative difference between the thermal coefficients of the two fibers, together with their similar strain sensitivity enables the simultaneous measurement of strain and temperature.

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