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Master's Dissertation
DOI
Document
Author
Full name
Caroline Cássia Alves
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Ribeirão Preto, 2018
Supervisor
Committee
Caiut, José Maurício Almeida (President)
Gonçalves, Rogéria Rocha
Nalin, Marcelo
Sousa Filho, Paulo Cesar de
Title in Portuguese
Sistemas compósitos luminescentes para geração de LASER em ambiente randômico
Keywords in Portuguese
1. LASER randômico
2. Terras raras
Abstract in Portuguese
Esse trabalho apresentou duas abordagens inovadoras no desenvolvimento de sistemas compósitos a partir de capilares de sílica, matrizes porosas e pós cerâmicos nanométricos visando sua utilização como precursores para sistemas lasers em ambiente randômicos. O laser randômico difere do laser convencional pela ausência de uma cavidade óptica que seleciona os modos ressonantes. No lugar desta, existe a presença de partículas ou poros que espalham a luz, e permitem que a radiação fique retida no material por tempo suficiente para que a amplificação na intensidade ocorra via emissão estimulada. Neste sentido, foram desenvolvidos diferentes compósitos luminescentes: primeiro; capilares de sílica fundida preenchidos com partículas espalhadoras e sistemas emissores (Rodamina B ou íons terras raras). Segundo, estruturas porosas de alumina e sílica obtidas via síntese template (a partir de fibras de celulose) e um sistema emissor a base de Rodamina B ou partículas luminescentes dopadas com íons terras raras. Os compósitos obtidos e caracterizados apresentaram diferentes desempenhos como meio laser randômico. O sistema obtido com capilar de sílica preenchido com partículas de boehmita dispersas numa matriz híbrida com Rodamina B apresentou emissão laser, com feedback coerente e lasing threshold igual à 34 mJ/mm2. Por outro lado, o sistema compósito de matriz porosa de alumina, sílica e Rodamina B apresentou emissão com feedback incoerente e lasing threshold igual à 62 mJ/mm2, a emissão coerente neste sistema só foi observada em condições especiais. Foram testadas nanopartículas de YVO4 dopadas com íons Eu3+, contudo somente a emissão espontânea foi observada nestes sistemas. Na etapa final do trabalho, nanopartículas de YVO4 dopadas com íons Nd3+ foram preparadas e caracterizadas, permitindo que novos sistemas compósitos sejam preparados em etapas futuras dentro do grupo de pesquisa.
Title in English
Composite luminescent systems with potential LASER application.
Keywords in English
1. LASER randômic
2. Rare lands
Abstract in English
This work presented two novel approaches to the development of composite systems from silica capillaries, porous matrices and nanometric ceramic powders, aiming its use as LASER precursors in random environments. Random lasers differ from conventional ones in the sense that in the former there is no optical cavity to select resonant modes. Instead, particles or pores scatter light, allowing radiation to be trapped inside the material long enough for amplification through stimulated emission to occur. Thus, two different luminescent composited were developed: first, fused silica capillaries filled with scattering particles and an emitting system (Rhodamine B dye or Rare Earth ions). Secondly, alumina and silica porous structures obtained via template synthesis (from cellulose fibres) and an emitting system based on Rhodamine B or Rare Earth ions-doped luminescent particles. The obtained composites were characterized and presented distinct performance as random laser medium. Fused silica capillaries filled with boehmite particles dispersed through a hybrid matrix and Rhodamine B presented laser emission with coherent feedback and a threshold of 34 mJ/mm². On the other hand, the alumina and silica porous matrix with Rhodamine B presented laser emission with incoherent feedback and a laser threshold of 62 mJ/mm², coherent emission in that system was only observed in special conditions. Eu3+-doped YVO4 nanoparticles were also tested, however only spontaneous emission was observed in these systems. In the final step of the work, Nd3+-doped YVO4 nanoparticles were prepared and characterised, allowing for new composites to be prepared in the future by this research group.
 
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Release Date
2021-02-19
Publishing Date
2019-06-26
 
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