TÃcnicas de Interferometria Ãptica aplicada à medicina, odontologia e comunicaÃÃes Ãpticas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

In the work described in this thesis, we used two different interferometric techniques, the coherent optical frequency domain reflectometry (COFDR), and the optical coherence tomography (OCT). Both techniques are based on the Michelson interferometer. They were applied to optical communications and to medical and dentistry imaging. We will give a general describe about optical interferometers. Also we will describe the interferometer development throughout science history, its different kinds and main applications. Different light sources can be used with these experiments and we will discuss about some of them. The basic operation of the COFDR and its applications to optical communications, particularly to optical amplifiers characterization, will be described. We will also describe about the optical amplifier based on thulium-doped fibers (TDFA) developed and characterized in our laboratories. We will discuss about the different pumping schemes that can be used, with one or two pumping lasers. We will show that the COFDR is a very efficient technique, not only to optimize the doped-fiber length, but also as a very important tool on the analysis of the amplifying dynamics, without having to cut the fiber to retrieve information. Together with other techniques, the TDFA we developed was totally characterized and a prototype was built. We will emphasize on the OCT technique from this point on. First, we will describe the technique, its characteristics, and main for applications in several medical fields. Dentistry is in constant development, and a growing usage of optical techniques to improve and precise diagnoses and treatments. OCT is an emerging diagnostic technology, and we will show results obtained from two experiments where it was used to characterize dental restorations and its viability to access information on the pulp of rat tooth was put to test. We will show that OCT can perform micro structural imaging of tissue morphology in situ without excision, and it can identify changes on the architectural morphology of hard and soft tissues. There is an important advance on the OCT technique we will discuss: Fourier domain detection. We will describe some experiments I took part during the internship at M.I.T, under Professor James Fujimotoâs orientation. He was one of the pioneer scientists to develop the OCT technique. Two variations if the OCT in the Fourier domain will be described, the spectral OCT and the swept source OCT, the last, similar to the COFDR technique, but applied to tomographic imaging. Two experiments, performed at M.I.T., will be described using the spectral OCT with direct applications to medical imaging; more specifically to ophthalmology. The first experiment is the development of a clinical instrument based on the spectral OCT to imaging the human retina, in vivo, on a clinical facility. Some results will be presented on normal and diseased eyes, showing the high quality the instrument can obtain. In the second experiment, we designed and constructed specialized high speed OCT instrument based on Fourier domain detection for imaging small animals like mice or rats. Our main objective was to introduce highâspeed, ultrahigh resolution OCT for performing nonâinvasive three dimensional imaging and mapping of the retina in small animal models. We will present the advantages on sensitivity and velocity of this technique compared to the time domain OCT. In the end, there will be a summary of all the work and we will draw our conclusions. The importance of these two techniques, COFDR and OCT, in each of its areas of application will be discussed, and we will talk about the continuity of the work we have done. The main objective of this thesis is to show how interferometric techniques based on devices developed more than one hundred year ago continue being updated and getting more and more importance on many areas (our everyday life). Science, especially optics, is getting more applied day after day. Laboratory research is transforming into commercial instruments faster and it is necessary for us to keep this rhythm. Multidisciplinary projects and the universityindustry association are the correct paths to keep science updated and productive

ASSUNTO(S)

fisica refletometria Ãptica coerente no domÃnio das freqÃÃncias tomografia por coerÃncia Ãptica coherent optical frequency domain reflectometry interferometria Ãptica detecÃÃo no domÃnio de fourier thulium doped fiber amplifier fourier domain detection optical coherence tomography optical interferometer amplificador a fibra dopada com tÃlio

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