Detecçăo e estudo da microvazăo de líquidos em fibras de cristal fotônico usando difraçăo na microestrutura

• Autor(a) principal: Santos, Felipe Argemi dos
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações do Mackenzie
• Texto Completo: http://dspace.mackenzie.br/handle/10899/24415
• topic: fibras de cristal fotônico; vazão de líquidos; difração; photonic crystal fibers; liquid flow; diffraction; CNPQ::ENGENHARIAS::ENGENHARIA ELETRICA

In this work, we introduce photonic crystal fibers and the study of liquid flow within those, by observing changes in the diffraction pattern generated in a a laser beam laterally incident in the fiber. By launching the laser beam perpendicularly onto the side of the photonic crystal fiber, a characteristic diffractive pattern is created by the cladding microstructure, which consists of a matrix of holes that run along the fiber. When the fiber is filled with a liquid with a refractive index close to that of silica, the diffractive pattern is reduced because the microstructure becomes virtually invisible to the laser. The diffraction pattern transition from an empty fiber to a completely filled one is not abrupt, taking place during several seconds. This is because not all the holes of the microstructure are filled at the same time, because they do not have exactly the same radii, and the displacement of the liquid depends on, among other factors, the radius of the structure along which it travels. By observing the diffractive pattern, one can, thus, determine the moment at which the fiber starts to be filled, via the beginning of the pattern change, until filling is complete, corresponding to the moment at which the diffractive pattern is completely changed. To determine the initial and final filling times accurately, and not influenced by the observer s subjective analysis, image processing techniques were used to evaluate the results. Through the times obtained it is possible to determine the largest and the shortest radius. The results of the size of the holes obtained by the time of filling, and the error in relation to the size observed by microscopy, will be presented. Finally, future work for improving the technique will be suggested.