2013
Autores
Ribeiro, RSR; Guerreiro, A; Ecoffet, C; Soppera, O; Jorge, PAS;
Publicação
FIFTH EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS
Abstract
This paper presents a study of optical forces acting on dielectric particles in media of distinct refractive index. The radiation pressure forces produced by optical tweezers are calculated using the finite difference time domain method as well as the Lorentz force on electric dipoles. The model considers a 2-dimension structure composed of a waveguide and a dielectric microparticle. Furthermore, the paper presents preliminary experimental results concerning the implementation of fiber optical tweezers system based on polymeric lensed fibers.
2014
Autores
Ribeiro, RSR; Queiros, RB; Ecoffet, C; Soppera, O; Oliva, A; Guerreiro, A; Jorge, PAS;
Publicação
OPTICAL TRAPPING AND OPTICAL MICROMANIPULATION XI
Abstract
This work reports a new type of optical fiber tweezers based on polymeric micro-lenses. The lenses are achieved by means of an economical and fast fabrication process, using an in-fiber photo-polymerization technique. The polymerization radiation is guided towards the fiber tip creating a polymeric waveguide. The method allows tailoring the geometry of the tip by adjusting the fabrication parameters. Furthermore, more complex shapes can be fabricated by exploring modal effects at the polymerization/trapping wavelengths, which can be used for different applications such as trapping, beam shaping and patterned illumination.
2014
Autores
Fernandes, CS; Rocco Giraldi, MTMR; Gouveia, CJ; Sousa, MJ; Costa, JCWA; Frazao, O; Jorge, PAS;
Publicação
SECOND INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS
Abstract
In this work, a remote curvature sensor using a standard OTDR as the interrogation system is presented. This approach uses a core diameter mismatch sensor which is formed by a short section of a multimode fiber, with a length of 3 mm, sandwiched between two singlemode fibers. In this case, the attenuation of the optical signal will vary as the fiber is bent allowing interrogating the sensor with OTDR technology. Preliminary results indicate a resolution range of similar to 0.0003 cm(-1), sensitivity in the range of similar to-208.46 dB/cm(-1) and a variation of 2.67 dB in the OTDR trace within the bend radius range.
2014
Autores
Cennamo, N; Coelho, L; Guerreiro, A; Jorge, PAS; Zeni, L;
Publicação
23RD INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS
Abstract
In this work we present a new low cost SPR (Surface Plasmon Resonance) sensor configuration based on efficient higher-order mode filtering in plastic multimode fibers, using a tapered POF (Plastic Optical Fiber) after the sensor system, without decreasing the sensitivity of the sensor. In particular, we present the experimental results obtained with this new configuration. The experimental results have shown as the tapered POF after the sensor system influences the performances in terms of refractive index range and Signal-to-Noise Ratio (SNR).
2013
Autores
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;
Publicação
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.
2014
Autores
Machado, C; Gouveia, C; Ferreira, J; Kovacs, B; Jorge, P; Lopes, L;
Publicação
2014 IEEE SENSORS
Abstract
We present a new and versatile sensor platform to readout the response of sensitive colorimetric films. The platform is fully self-contained and based on a switched dual-wavelength scheme. After filtering and signal processing, the system is able to provide self-referenced measures of color intensity changes in the film, while being immune to noise sources such as ambient light and fluctuations in the power source and in the optical path. By controlling the power and the switching frequency between the two wavelengths it is possible to fine tune the output gain as well as the operational range of the sensor for a particular application, thus improving the signal conditioning. The platform uses a micro-controller that complements the analog circuit used to acquire the signal. The latter pre-amplifies, filters and conditions the signal, leaving the micro-controller free to perform sensor linearization and unit conversion. By changing the sensitive film and the wavelength of the light source it is possible to use this platform for a wide range of sensing applications.
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