143 resultados para Optical absorption


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

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Pós-graduação em Ciência dos Materiais - FEIS

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Pós-graduação em Ciência dos Materiais - FEIS

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Triacrylate resins are widely used to fabricate 3D microstructures, photonic crystals and optical devices. These resins can be doped with photosensitive materials like Disperse Red 1 (DR1), an Azo dye that changes its molecular configuration from trans to cis (photoisomerisation) with variations in their optical absorption spectrum when irradiated with ultraviolet or visible light. The reversibility of this process is thermally activated and occurs when the molecule remains at dark. In this work was prepared a 1:1 mixture of ethoxylated-6-trimethylolpropane (SR499) and tris-2-hydroxyethyl-isocyanurate (SR368) triacrylate resins, plus photoinitiator Lucirin TPOL, forming a UV curable polymeric matrix doped with DR1. Thin films were deposited onto glass slides by spin-coating technique. The films showed photochromic effect when illuminated with a low power diode laser (450 nm and 50mW/cm2). This effect is reversible after sample is left in dark. Thermochromic effect was evaluated by optical absorption measurements in the range of 40 to 140oC, heating the samples in-situ

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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

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Results of photoluminescence measurements for natural and synthetic alexandrite (BeAl2O4:Cr3+) are presented, where the samples are excited by the 488 nm line of an Ar+ laser, at different temperatures. The main issue is the analysis of the Cr3+ transition in the chrysoberyl matrix (BeAl2O4), with major technological application as active media for laser action. Results indicate anomalous behavior of Cr3+ transition depending on the measurement temperature. A simple model to explain the phenomena is suggested.

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Perylene tetracarboxylic derivatives (PTCDs) display exceptionally high two-photon absorption (2PA) cross-sections (6, see Figure). In addition, the 2PA saturation behavior and strong two-photon-pumped fluorescence suggest that PTCD compounds may be attractive candidates for applications in optical limiting and two-photon-pumped upconversion lasing.