2019
Authors
Amorim, VA; Viveiros, D; Maia, JM; Marques, PVS;
Publication
FOURTH INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS
Abstract
The fabrication of optical waveguides with femtosecond laser direct writing is reported in two materials, Suprasil1 and Eagle2000. The influence of typical fabrication parameters, such as pulse energy and scan velocity, on the waveguide's spectral characteristics is explored from 500 to 1700 nm. Tests conducted in Suprasil1 evidence a strong presence of Rayleigh scattering, hindering the production of low-loss waveguides at short wavelengths. On the other hand, optical waveguides fabricated in Eagle2000 exhibited lower insertion losses at short wavelengths, enabling the fabrication of low-loss broadband optical waveguides with a two order of magnitude higher scan velocity when compared with Suprasil1.
2019
Authors
Carneiro, I; Carvalho, S; Henrique, R; Oliveira, L; Tuchin, VV;
Publication
IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS
Abstract
In this paper, we describe a simple and indirect method to evaluate the kinetics of the optical properties for biological tissues under optical clearing treatments. We use the theoretical formalism in this method to process experimental data obtained from colorectal muscle samples to evaluate and characterize the dehydration and refractive index matching mechanisms.
2019
Authors
Viveiros, D; Maia, JM; Amorim, VA; Jorge, PAS; Marques, PVS;
Publication
FOURTH INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS
Abstract
A femtosecond laser direct writing system was developed to explore the fabrication of periodic structures in optical fibers. The possibility to write type I first- and second-order Bragg gratings in the same single-mode fiber (SMF-28e), with reflectivities of 99.6 % and 59.3 %, respectively, is presented. The fabrication of structures (waveguides and grating) in a coreless and in a SMF-28e fiber was first demonstrated, and the gratings were then exposed to a thermal annealing up to 1000 degrees C. The FBG inscribed in the SMF-28e fiber presents thermal stability at temperatures of 800 degrees C and a temperature sensitivity of 14.34 pm/degrees C was determined.
2019
Authors
Monteiro, CS; Vaz, A; Viveiros, D; Linhares, C; Tavares, SMO; Mendes, H; Silva, SO; Marques, PVS; Frazao, O;
Publication
SEVENTH EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS (EWOFS 2019)
Abstract
Power transformers are at the core of power transmission systems. The occurrence of system failure in power transformers can lead to damage of adjacent equipment and cause service disruptions. Structural and electrical integrity assessment in real time is of utter importance. Conventional techniques, typically electrical sensors or chemical analysis, present major drawbacks for real-time measurements due to high electromagnetic interference or for being time-consuming. Optical fiber sensors can be used in power transformers, as they are compact and immune to electromagnetic interferences. In this work, an optical fiber sensor composed by 2 fiber Bragg gratings, attached in a cantilever structure was explored. The prototype was developed with a 3D printer using a typical filament (ABS) that enable a fast and low-cost prototyping. The response of the sensor to vibration was tested using two different vibration axes for frequencies between 10 and 500 Hz. Oil compatibility was also studied using thermal aging and electrical tests. The studies shown that ABS is compatible with the power transformer mineral oil, but the high working temperatures may lead to material creeping, resulting in permanent structural deformation.
2019
Authors
Maia, JM; Amorim, VA; Viveiros, D; Marques, PVS;
Publication
EPJ Web of Conferences
Abstract
2019
Authors
Guerreiro, A; Apolinario, A; Lopes, A; Hierro Rodriguez, A; Aguilar, G; Baptista, JM; Silva, NA; Frazao, O; Quiterio, P; Jorge, P; Rodrigues, P; Moraes, SS; Silva, S; Ferreira, TD; Santos, JL; Araujo, JP;
Publication
FOURTH INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS
Abstract
We present the design, fabrication and optical characterization of functional metamaterials for optical sensing of Hydrogen based on inexpensive self-assembly processes of metallic nanowires integrated in nanoporous alumina templates([37-42]). The optical properties of these materials strongly depend on the environmental concentration or partial pressure of hydrogen and can be used to develop fully optical sensors that reduce the danger of explosion. Optical metamaterials are artificial media, usually combining metallic and dielectric sub-wavelength structures, that exhibit optical properties that cannot be found in naturally occurring materials. Among these, functional metamaterials offer the added possibility of altering or controlling these properties externally after fabrication, in our case by contact with a hydrogen rich atmosphere. This dependency can be used to design([43-45]) and develop optical sensors that respond to this gas or to chemical compounds that contain or release hydrogen. In this paper we present some designs for hydrogen functional metamaterials and discuss the main parameters relevant in the optimization of their response.
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