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Master's Dissertation
DOI
https://doi.org/10.11606/D.76.2020.tde-15052020-133107
Document
Author
Full name
Gaston Lozano Calderón
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2020
Supervisor
Committee
Marega Junior, Euclydes (President)
Ferri, Fabio Aparecido
Ribeiro, Sidney José Lima
Title in English
White light emission under 980 nm and Judd-Ofelt analysis of tellurite-zinc glasses doped with Er3+-Yb3+-Tm3+
Keywords in English
Energy transfer
Judd-Ofelt
Micro-parameters
Rare-earths
Tellurite
Up-conversion
White light
Abstract in English
In this dissertation, tellurite-zinc glasses doped with Tm3+, Yb3+ and Er3+ were fabricated by conventional melt-quenching method and characterized by absorption spectroscopy, refractive index, lifetime measurements, excitation, luminescence and up-conversion spectroscopy. Tunable white to blue light emission based on the colour mixing of red, green and blue light was observed in the triply-doped samples via up-conversion under 980 nm and by adjusting the laser excitation intensity. The balancing of the relative intensity of each colour is provided by the energy transfer process between the rare-earth ions. Moreover, luminescence spectroscopy was performed with a 405 nm laser to further understand the energy transfer mechanism. According to the Judd-Ofelt theory, the intensity parameters (Ω2, Ω4 and Ω6) of Er3+ and Tm3+ for all samples present the trend Ω2 < Ω4 < Ω6. These parameters are related to the bonding and local structure in the vicinity of the rare-earth ions, which give information regarding to physical and chemical properties. The spectroscopic parameters were calculated with the Judd-Ofelt theory and the energy transfer micro-parameters (critical radius of interaction and energy transfer coefficient) were determined by the Dexter model. Such results shall be used to give a comprehensive explanation for the energy transfer process between these rare earth ions.
Title in Portuguese
Emissão de luz branca sob 980 nm e análise de Judd-Ofelt de vidros de zinco-telurito dopados com Er3+-Yb3+-Tm3+
Keywords in Portuguese
Conversão ascendente
Judd-Ofelt
Luz branca
Micro-parâmetros
Telurito
Terras raras
Transferência de energia
Abstract in Portuguese
Nesta dissertação, vidros de telurito-zinco dopados com Tm3+, Yb3+ e Er3+ foram fabricados pelo método convencional de fusão-resfriamento e caracterizados através da espectroscopia de absorção, índice de refração, medidas de tempos de vida, espectrocopia de excitação, de luminescência e de conversão ascendente. Luz branca até azul sintonizável baseada na mistura de cores vermelha, verde e azul, foi observada nas amostras triplemente dopadas via conversão ascendente sob 980 nm e ajustando a intensidade de excitação do laser. O equilíbrio da intensidade relativa de cada uma das cores é determinado pelos procesos de trasnferência de energia entre os íons de terras raras. Ademais, a espectroscopia de luminescência foi realizada com um laser de 405 nm. De acordo com a teoria de Judd-Ofelt, os parâmetros de intensidade (Ω2, Ω4 e Ω6) do Er3+ e Tm3+para todas as amostras apresentam a tendência Ω2 < Ω4 < Ω6. Esses parâmetros estão relacionados à ligação e a estrutura local nas proximidades dos íons de terras raras, os quais fornecen informações sobre propriedades físicas e químicas. Os parâmetros espectroscópicos foram calculados a través da teoria de Judd-Ofelt e os micro-parâmetros de transferência de energia (raio crítico de interação e coeficiente de transferência de energia) foram determinados pelo modelo de Dexter. Tais resultados são utilizados para fornecer uma explicação compreensiva do processo de transferência de energia entre os íons de terras raras.
 
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Publishing Date
2020-05-21
 
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