2010
Autores
Rego, G;
Publicação
JOURNAL OF OPTICS
Abstract
We present an overview of the applications of the electric arc technique related to optical fibre technology. The use of arc discharges ranges from the well-known fibre splicing, going through the fabrication of basic devices such as fibre tapers and microspheres, to tailoring the spectra of UV-induced gratings such as in the apodization of fibre Bragg gratings and also in the fabrication of phase-shifted and sampled fibre Bragg gratings. However, in the past decade a topic more intensively investigated was probably long-period fibre gratings. Therefore, some devices based on arc-induced gratings, namely, phase-shifted and step-changed gratings and bandpass filters are discussed. We also present an electrically insulated thermocouple assembled in situ using arc discharges. This sensor is very useful in the determination of the temperature attained by the fibre during an arc discharge, this property being fundamental for the discussion of the mechanisms of formation and for the understanding of the thermal properties of arc-induced devices.
2010
Autores
Ferreira, RAS; Vicente, C; Xavier, LR; Fernandes, V; Carlos, LD; Andre, PS; Pecoraro, E; De Zea Bermudez, V; Monteiro, P; Marques, PVS;
Publicação
2010 12th International Conference on Transparent Optical Networks, ICTON 2010
Abstract
In this paper, direct UV-laser writing was used to produce channel waveguides and diffraction gratings on thin films of siliceous-based organic-inorganic hybrid materials. The optical quality of the films surface was studied by light scattering measurements. The produced Y-power splitters, optical filters and Fabry-Perot cavities were experimentally characterized for propagation in the near infrared spectral region. © 2010 IEEE.
2010
Autores
Ghasempour, A; Leite, AMP; Alexandre, D; Reynaud, F; Marques, PVS; Garcia, PJV; Moreira, PJ;
Publicação
OPTICS EXPRESS
Abstract
Integrated optics coaxial two, three and four telescope beam combiners have been fabricated by hybrid sol-gel technology for astronomical applications. Temporal and spectral analyses of the output interferometric signal have been performed, and their results are in mutual good agreement. The results of the characterization method employed are cross-checked using contrast measurements obtained independently, demonstrating that the chromatic differential dispersion is the main contributer to contrast reduction. The mean visibility of the fabricated devices is always higher than 95 %, obtained using a source with spectral bandwidth of 50 nm. These results show the capability of hybrid sol-gel technology for fast prototyping of complex chip designs used in astronomical applications. (C) 2010 Optical Society of America
2010
Autores
Ghasempour, A; Leite, AMP; Alexandre, D; Reynaud, F; Marques, PVS; Garcia, PJV;
Publicação
OPTICAL AND INFRARED INTERFEROMETRY II
Abstract
Hybrid sol-gel technology was used for fabrication of prototypes of coaxial two, three and four telescopes beam combiners for astronomical applications. These devices were designed for the astronomical J-band and have been characterized using an optical source with emission centered at 1265 nm and with a spectral FWHM of 50 nm. Interferometric characterization of the two, three and four beam combiners, showed average contrasts respectively higher than 98%, 96% and 95%. Interferometric spectral analysis of the beam combiners revealed that the chromatic differential dispersion is the main contributor to the observed contrast decay in the latter cases. The laser direct writing technique was used for fabrication of a coaxial two beam combiner on sol-gel material; it showed a contrast of 95%. The measured high contrast fringes confirm that the procedures used lead to performant IO beam combiners. These results demonstrate the capabilities of the hybrid sol-gel technology for fast prototyping of complex chip designs for astronomical applications.
2010
Autores
Tafulo, PAR; Ferro, M; Guerreiro, A; Gonzalez Aguilar, G;
Publicação
APPLIED SURFACE SCIENCE
Abstract
In this paper is described an easy, one-pot synthesis of ZnO hollow spheres with sizes ranging from 300 nm to 500 nm, by spin-coating deposition on aluminum substrate. Simplified models explaining the shape formation based on film-substrate interaction are discussed. The characteristic size and shape of the nanostructures obtained by the described method and the properties of ZnO as a low-cost biocompatible material make this methodology of synthesis interesting for a wide range of applications including optoelectronics, catalysis and (bio)sensors.
2010
Autores
Martins, AM; Guerreiro, A; Mendonca, JT; Vieira, VR;
Publicação
PHYSICAL REVIEW A
Abstract
We investigate the generation of entanglement between the axial degrees of freedom of electrons confined in separated locations in planar Penning traps. We show that there are two different sources of entanglement: one is related with the mechanism of switching on and off the electrical coupling between the two electrons, and the other is due to the two-quanta-transition term of the coupling interaction. We show that the degree of entanglement can be controlled by adjusting the strength of the coupling between the traps and the time of interaction. We show that the coupled electrons behave as a temporal active interferometer.
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