Evaluation of the thermal diffusivity of vegetable oils during frying by Thermal Lens Spectrometry

In this work we report on the use of the Thermal Lens method to verify the evolution of the thermal diffusivity of sunflower and soybean vegetable oils utilized in preparation of twenty five snacks portions. Our results show that the thermal diffusivity for sunflower oil does not change between 1 and 25 portions of fried snacks. By another hand, the soybean thermal diffusivity exhibits a little decrease for higher portion of fried snacks, indicating that for this oil the triglyceride level is reduced as a degradation process.

Thermal-optical properties of Ga : La : S glasses measured by thermal lens technique

In this work the quantitative theoretical treatment for two beam mode mismatched thermal lens spectrometry is applied to investigate the thermo-optical properties of chalcohalide (chalcolgenides and halides mixture) glasses. For the three kinds of glass studied the thermal diffusivity varied between 2.5 and 2.7 x 10(-3) cm(2) s(-1). Using these results and supposing Dulong-Petit specific heats we estimated the thermal conductivity and temperature ratio of optical path length (ds/dT) and temperature coefficient of refractive index (dn/dT). All samples had positive ds/dT(similar to 3.3 x 10(-6) K-1) and negative dn/dT (similar to -26 x 10(-6) K-1). The difference between these parameters and the change of signal are consequences of the expansion coefficient (13 x 10(-6) K-1) and refractive index (n similar to 2.6) of chalcohalides. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Relation among optical, thermal and thermo-optical properties and niobium concentration in tellurite glasses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Thermo-optical characterization of tellurite glasses by thermal lens, thermal relaxation calorimetry and interferometric methods

In this work the thermal lens, thermal relaxation calorimetry and interferometric methods are applied to investigate the thermo-optical properties of tellurite glasses (in mol%: 80TeO(2)-20 Li2O(TeLi), 80TeO(2)-15Li(2)O-5TiO(2) (TeLiTi-5) and 80TeO(2)-10Li(2)O-10TiO(2) (TeLiTi-10)). Thermal diffusivity, thermal conductivity, specific heat and the temperature coefficients of refractive index, optical path length, thermal expansion and electronic polarizability were determined. The use of three independent methods was useful for a complete characterization of the studied tellurite glasses. In addition, our results showed that the thermal expansion coefficient and the temperature coefficient of the optical path length (dS/dT) were significantly modified with the introduction of titanium, which may be relevant for the application of these glasses in the photonic area. (c) 2006 Elsevier B.V. All rights reserved.

Time-resolved Z-scan and thermal lens measurements in Er+3 and Nd+3 doped fluoroindate glasses

In rare earth ion doped solids, a resonant non-linear refractive index, n2, appears when the laser pumps one of the ion excited states and the refractive index change is proportional to the excited state population. In these solids there are usually thermal and non-thermal lensing effects, where the non-thermal one is due to the polarizability difference, Δα, between excited and ground states of the ions. We have used the time resolved Z-scan and a mode-mismatched thermal lens technique with an Ar+ ion laser in Er+3 (20ZnF2-20SrF2-2NaF-16BaF2-6GaF3-(36 - x)InF3-xErF3, with x= 1, 2, 3 and 4 mol%) and Nd+3 (20SrF2-16BaF2-20ZnF2-2GdF3-2NaF-(40 - x)InF3-xNdF3, with x = 0.1, 0.25, 0.5-1 mol%) doped fluoroindate glasses. In both samples we found that the non-linear refraction is due to the thermal effect, while the non-thermal effect is negligible. This result indicates that in fluoride glasses Δα is very small (less than 10-26 cm3). We also measured the imaginary part of the non-linear refractive index (n″2) due to absorption saturation.

Two-wavelength whole-field interferometry setup for thermal lens study

In this paper we present a new approach for thermal lens analysis using a two-wavelength DSPI (Digital Speckle Pattern Interferometry) setup for wavefront sensing. The employed geometry enables the sensor to detect wavefronts with small phase differences and inherent aberrations found in induced lenses. The wavefronts was reconstructed by four-stepping fringe evaluation and branch-cut unwrapping from fringes formed onto a diffusive glass. Real-time single-exposure contour interferograms could be obtained in order to get discernible and low-spacial frequency contour fringes and obtain low-noise measurements. In our experiments we studied the thermal lens effect in a 4% Er-doped CaO-Al2O3 glass sample. The diode lasers were tuned to have a contour interval of around 120 μm. The incident pump power was longitudinally and collinearly oriented with the probe beams. Each interferogram described a spherical-like wavefront. Using the ABCD matrix formalism we obtained the induced lens dioptric power from the thermal effect for different values of absorbed pump power. © 2012 Copyright SPIE.

Luminescence quantum efficiency at 1.5 μm of Er3+-doped tellurite glass determined by thermal lens spectroscopy

Erbium doped tellurite glasses (TeO2 + Li2O + TiO2) were prepared by conventional melt-quenching method to study the influence of the Er3+ concentration on the luminescence quantum efficiency (η) at 1.5 μm. Absorption and luminescence data were used to characterize the samples, and the η parameter was measured using the well-known thermal lens spectroscopy. For low Er3+ concentration, the measured values are around 76%, and the concentration behavior of η shows Er-Er and Er-OH- interactions, which agreed with the measured lifetime values. © 2013 Elsevier B.V. All rights reserved.

Inversion in the temperature coefficient of the optical path length close to the glass transition temperature in tellurite glasses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Photothermal Study of Two Different Nanofluids Containing SiO2 and TiO2 Semiconductor Nanoparticles

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação óptica de vidros teluritos preparados com Er3+ e Er3+/Yb3+ para aplicação em fotônica

Pós-graduação em Ciência dos Materiais - FEIS

Spectroscopic and thermal characterization in poly(p-phenylene vinylene)/sol-gel silica sample

The absorption and luminescence spectra for the poly(p-phenylene vinylene)/sol-gel silica with different thermal treatments were measured. A considerable increase in the luminescence was observed for the polymer introduced into SiO2 matrix with thermal treatment at 120 degreesC. The thermal diffusivity of these samples was measured using the thermal lens technique, and the obtained value 3.3 x 10(-5) cm(2)/s (sample treated at 37 degreesC) is practically independent of the thermal treatment (37-150 degreesC). (C) 2003 Elsevier B.V. All rights reserved.

On observation of the downconversion mechanism in Er3+/Yb3+ co-doped tellurite glass using thermal and optical parameters

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Simple and versatile heterodyne whole-field interferometer for phase optics characterization

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Síntese e caracterização de vidros teluritos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Propriedades ópticas de materiais híbridos de sílica dopados com nanocristais de CdSe/ZnS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)