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Monitoring of oxidation phases of copper thin films using long period fiber gra...
Luís Carlos Coelho; Agostinho Moreira,JA; Tavares,PB; José Luís Santos; Diana Viegas; José AlmeidaLong period fiber gratings (LPFGs) were used to monitor the characteristics of copper (Cu) thin films when annealed in air atmosphere up to similar to 680 degrees C. The wavelength and the optical power shift of the resonant bands of the LPFGs when coated with the Cu thin films, were measured as a function of the annealing temperature, and were found to exhibit a different evolution comparing to a bare LPFGs. T...
Characterization of zinc oxide coated optical fiber long period gratings with i...
Luís Carlos Coelho; Diana Viegas; José Luís Santos; José AlmeidaA fiber-optic refractive index (RI) sensor based on a long period fiber grating (LPFG) coated with a zinc oxide (ZnO) thin film was fabricated and characterized. A method to overcoat the LPFG's with a homogeneous ZnO thin films was developed. Characterization of ZnO thin films, deposited simultaneously on silicon (Si) planar substrates, was performed using Scanning Electron Microscope, Energy Dispersive X-ray S...
Aptamer-based fiber sensor for thrombin detection
Luís Carlos Coelho; José Almeida; José Luís Santos; Pedro Jorge; Martins,MCL; Diana Viegas; Queiros,RBThe detection of thrombin based on aptamer binding is studied using two different optical fiber-based configurations: long period gratings coated with a thin layer of titanium dioxide and surface plasmon resonance devices in optical fibers coated with a multilayer of gold and titanium dioxide. These structures are functionalized and the performance to detect thrombin in the range 10 to 100 nM is compared in tra...
Hydrogen sensing via anomalous optical absorption of palladium-based metamaterials
Hierro Rodriguez,A; Leite,IT; Rocha Rodrigues,P; Fernandes,P; Araujo,JP; Pedro Jorge; José Luís Santos; Teixeira,JM; Ariel GuerreiroA palladium (Pd)-based optical metamaterial has been designed, fabricated and characterized for its application in hydrogen sensing. The metamaterial can replace Pd thin films in optical transmission schemes for sensing with performances far superior to those of conventional sensors. This artificial material consists of a palladium-alumina metamaterial fabricated using inexpensive and industrial-friendly bottom...
Fabrication and Characterization of Metal Oxide-Coated Long-Period Fiber Gratings
Luís Carlos Coelho; José Luís Santos; Diana Viegas; José AlmeidaSensors based on long-period fiber gratings (LPFGs) over coated with metal oxide were fabricated and characterized for refractive index (RI) sensing. Oxidation of Ni, Ti, Al, and Cr was monitored in real time by following the features of the LPFG attenuation band. Themetals were deposited simultaneously on top of Si substrates for further chemical and morphological analysis. Wavelength sensitivities (nm/RIU) of...
Analysis of a Plasmonic Based Optical Fiber Optrode With Phase Interrogation
Hamed Moayyed; Leite,IT; Luís Carlos Coelho; José Luís Santos; Diana ViegasOptical 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 res...
FIBER OPTIC DISPLACEMENT SENSOR BASED ON A DOUBLE-REFLECTING OTDR TECHNIQUE
Rocco Giraldi,MTMR; Fernandes,CS; Marta Sofia Ferreira; de Sousa,MJ; Pedro Jorge; Costa,JCWA; José Luís Santos; Orlando FrazãoIn this work, it is proposed a technique to implement an intensity sensor based on the generation of a double-reflecting (ghost) signal in optical time domain reflectometry (OTDR). The intensity sensor is supported by a singlemode-multimode-singlemode (SMS) fiber structure combined with a fiber loop mirror (FLM). The results of the displacement sensitivity show linear behavior for both the first-reflecting and ...
Theoretical Study of Phase-Interrogated Surface Plasmon Resonance Based on Opti...
Hamed Moayyed; Leite,IT; Luís Carlos Coelho; José Luís Santos; Diana ViegasThis work reports the theoretical investigation of optical fiber surface plasmon resonance sensors incorporating an internal metallic layer of silver covered with an oxide layer. This research is supported by the application of an effective analytical model combining geometrical optics with the transfer matrix theory for stratified optical media. Different oxide materials like titanium dioxide, silicon dioxide,...
Fabry-Perot cavity based on silica tube for strain sensing at high temperatures
Marta Sofia Ferreira; Paulo Roriz Oliveira; Bierlich,J; Kobelke,J; Wondraczek,K; Aichele,C; Schuster,K; José Luís Santos; Orlando FrazãoIn this work, a Fabry-Perot cavity based on a new silica tube design is proposed. The tube presents a cladding with a thickness of similar to 14 mu m and a hollow core. The presence of four small rods, of similar to 20 mu m diameter each, placed in diametrically opposite positions ensure the mechanical stability of the tube. The cavity, formed by splicing a section of the silica tube between two sections of sin...
Multimodal Interferometer Based on a Suspended Core Fiber for Simultaneous Meas...
Rota Rodrigo,S; Lopez Amo,M; Kobelke,J; Schuster,K; José Luís Santos; Orlando FrazãoIn this study, a multimodal interferometer based on a suspended core photonic crystal fiber (PCF) for simultaneous strain and temperature measurements is proposed. The structure is also employed for angle measurements. The sensor comprises a 3-mm-suspended core PCF between SMFs and is based on the combination of two multimodal interferences with different frequency fringe patterns. The interferometric patterns ...