2013
Authors
Ribeiro, RSR; Jorge, PAS; Guerreiro, A;
Publication
8TH IBEROAMERICAN OPTICS MEETING AND 11TH LATIN AMERICAN MEETING ON OPTICS, LASERS, AND APPLICATIONS
Abstract
The intensity profile of a focused beam of light can exert small drift forces on particles with a few microns and even smaller, which can be used to confine or manipulate them. Optical trapping has several applications, in particular it has been adopted as a powerful tool in biology, allowing, for instance to manipulate in vivo single cells. A wide variety of optical setups have been implemented to optically trap microscopic bodies, however, the single beam trap using a tightly focused Gaussian beam continues to be the most used. Recent developments introduced an alternative to bulk optical trapping systems based on lensed optical fibers. This work presents simulations showing new designs of fiber optic and 2D waveguide tweezers based on studies of the forces acting on dielectric particles immersed in media with a distinct refractive index, which take into account the refractive index and structure of the particles.
2013
Authors
Ribeiro, RSR; Guerreiro, A; Ecoffet, C; Soppera, O; Jorge, PAS;
Publication
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.
2013
Authors
Moura, JPP; Silva, SO; Becker, M; Rothardt, M; Bartelt, H; Frazao, O;
Publication
FIFTH EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS
Abstract
A simple optical inclinometer based on phase-shifted Bragg grating in a taper configuration is proposed. The phase-shifted FBG was fabricated using a DUV femtosecond laser technique in the taper region. The sensing head was characterized for different angle curvatures and also to strain. The angle and strain sensitivities of the inclinometer are 13.15 pm/degree and 8.96 pm/mu epsilon.
2013
Authors
Ferreira, MS; Roriz, P; Silva, SO; Santos, JL; Frazao, O;
Publication
OPTICAL FIBER TECHNOLOGY
Abstract
This paper presents an overview of optical fiber sensors based on Fabry-Perot interferometers with a focus on high temperature applications. The next generation of these fiber types interferometers are based in photonic crystal fibers, microfabrication as well as by chemical etching of special structures. High temperature measurements with linear behavior are observed namely in un-doped fibers, i.e., with a pure silica composition. Three new configurations are presented as possible solutions to be considered in extreme conditions.
2013
Authors
Balogh, K; Jesus, JM; Gouveia, C; Domingues, JO; Markovics, A; Baptista, JM; Kovacs, B; Pereira, CM; Borges, MT; Jorge, PAS;
Publication
8TH IBEROAMERICAN OPTICS MEETING AND 11TH LATIN AMERICAN MEETING ON OPTICS, LASERS, AND APPLICATIONS
Abstract
A novel optical fiber sensor is presented for measuring dissolved CO2 for water quality monitoring applications, where the optical signal is based either on refractive index changes or on color change. The sensing chemistry is based on the acid-basic equilibrium of 4-nitrophenol, that is converted into the anionic form by addition quaternary ammonium hydroxide. The CO2 sensitive layer was characterized and tested by using simple absorbance/reflectance measurement setups where the sensor was connected to a fiber optic CCD spectrometer. A prototype simulating a real shallow raceway aquaculture system was developed and its hydraulic behavior characterized. A commercially available partial-pressure-NDIR sensor was used as a reference for dissolved CO2 tests with the new optical fiber sensor under development. Preliminary tests allowed verifying the suitability of the new optical sensor for accurately tracking the dissolved carbon dioxide concentration in a suitable operation range. Direct comparison of the new sensor and the reference sensor system allowed to demonstrate the suitability of the new technology but also to identify some fragilities there are presently being addressed.
2013
Authors
Pontes, MJ; Coelho, TVN; Carvalho, JP; Santos, JL; Guerreiro, A;
Publication
8TH IBEROAMERICAN OPTICS MEETING AND 11TH LATIN AMERICAN MEETING ON OPTICS, LASERS, AND APPLICATIONS
Abstract
This work discusses remote fiber sensors enabled by optical amplification. Continuous wave numerical modeling based on the propagation of pumps and signal lasers coupled to optical fibers explores Raman amplification schemes to predict the sensor's behavior. Experimental analyses report the results to a temperature remote optical sensor with 50 km distance between the central unit and the sensor head. An electrical interrogation scheme is used due to their low cost and good time response. Different architectures in remote sensor systems are evaluated, where diffraction gratings are the sensor element. A validation of calculated results is performed by experimental analyses and, as an application, the noise generated by Raman amplification in the remote sensors systems is simulated applying such numerical modeling. The analyses of sensors systems based on diffraction gratings requires optical broadband sources to interrogate the optical sensor unit, mainly in long period gratings that shows a characteristic rejection band. Therefore, the sensor distance is limited to a few kilometers due to the attenuation in optical fibers. Additional attenuation is introduced by the sensor element. Hence, to extend the distance in the optical sensor system, the optical amplification system is needed to compensate the losses in the optical fibers. The Raman amplification technology was selected mainly due to the flexibility in the gain bandwidth. The modeling can be applied to sensor systems that monitor sites located at long distances, or in places that the access is restricted due to harsh environment conditions in such cases conventional sensors are relatively fast deteriorated.
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