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Master's Dissertation
DOI
https://doi.org/10.11606/D.76.1998.tde-06042009-115559
Document
Author
Full name
Fernando Fuzinatto Dall' Agnol
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1998
Supervisor
Committee
Zilio, Sergio Carlos (President)
Catunda, Tomaz
Vieira Junior, Nilson Dias
Title in Portuguese
Aplicação da técnica de varredura-Z para a determinação de parâmetros térmicos.
Keywords in Portuguese
Lente térmica
Óptica não-linear
Varredura-Z
Abstract in Portuguese
A técnica de varredura-z tem sido bastante utilizada para a determinação do índice de refração não-linear (n2) em meios transparentes. Apresentamos neste trabalho uma análise teórica e resultados da técnica de varredura-z por reflexão, visando o estudo de efeitos térmicos em amostras que possuem coeficientes de absorção muito grandes. Extensões à técnica, tais como: a varredura-z resolvida no tempo e varredura-z resolvidas em freqüência puderam ser aplicadas para medir efeitos térmicos, pois estes são relativamente lentos nos materiais que medimos (água, polímero e vidro). Das componentes linear e quadrática da evolução temporal da transmitância, ou, da segunda componente de Fourier de curvas obtidas em duas freqüências, pode-se extrair parâmetros térmicos como: a capacidade térmica por unidade de massa e a difusividade térmica. Propriedades térmicas são de grande interesse na usinagem de peças, e em estudos sobre tensões estruturais e novos materiais. Pela teoria aqui desenvolvida, dada as constantes térmicas, é possível distinguir os efeitos térmicos e eletrônicos nas amostras que apresentam os dois.
Title in English
Z-scan technique to evaluate thermal parameters.
Keywords in English
Non-linear optics
Thermal lens
Z-scan
Abstract in English
The Z-Scan technique is the most popular one for the determination of the nonlinear index of refraction (n2) of transparent media. In this work we present a theoretical analysis and results of the reflection z-scan technique, aiming the research of thermal effects in highly absorbing materials. Extensions of the technique, such as the time resolved z-scan and the frequency resolved z-scan could be applied to measure thermal effects because they are relatively slow in the materials that we have measured (water, polystyrene and glass). From the linear and quadratic terms of the transmittance time evolution, or, from the second Fourier component of curves obtained in two frequencies, one can extract thermal parameters like: the heat capacity per unit mass and the thermal diffusion coefficient. Thermal properties are of great interest in the manufacture of pieces, and in the study of structure strains and new materials. By the theory presented here, if thermal constants are given, one can distinguish between thermal and electronic effects in samples that present both.
 
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Publishing Date
2009-04-07
 
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