CRESCIMENTO E CARACTERIZAÇÃO DE FIBRAS MONOCRISTALINAS DE FLUORETOS DO TIPO LiY1-xTRxF4 (TR = TERRAS-RARAS) / GROWTH AND CHARACTERIZATION OF FLUORIDE CRYSTALLINE FIBRES TYPE LiY1-xTRxF4 (RE = RARE-EARTH)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

In this work we present the growth and characterization of LiF and pure and rare-earth doped (Er and Nd) yttrium-lithium tetra-fluoride (LiYF4 or YLF) by the micro-pulling-down technique (µ-PD). The use of this technique is original for the present purpose. A m-PD prototype in the resistive mode was firstly built to understand the most important operational parameters. A commercial equipment was later installed and specifically modified to grow fluoride fibres. Regular and transparent single-crystalline fibres of LiF (diameter of 0.6 mm and length up to 150 mm) were obtained. LiF crystalline fibres as a potential laser media presented the same spectroscopic properties of bulk crystals. The influence of capillary and crucible shapes, growth atmosphere and start composition stoichiometry on the growth process of YLF fibers were also investigated. In general, the fluorides are very sensitive to moisture contamination. The growth atmosphere plays an important role on the stoichiometry deviation. Since this fluoride melts incongruently, any compositional changes inflences the solidification behavior of the material. Additionally, a limited pulling rate is required to the YLF phase formation and to the compositional homogeneity along the fiber. Homogeneous and regular section YLF fibres, with diametres between 0.5 to 0.8 mm and up to 60 mm in length, were obtained in a suitable and reproducible growth process. Er-doped (with nominal concentration of 10 and 40 mol%) and Nd-doped (with nominal concentration of 1.7 mol%) fibres were also successfully grown. Er-doped fibres were crack-free and the dopant concentration was practically uniform along the YLF phase. However, Nd–doped fibres presented a short initial transient in its concentration. The Nd distribution coefficient was evaluated as 0.58 for the YLF fibre. This value is greater than those estimated for YLF bulk crystals grown by normal freezing processes. The optical properties of the YLF:Nd fibres were similar to those observed in bulk crystals, which drive us to consider the YLF:Nd fibres as an important material to build compact all-solid-state lasers directly pumped by diodes.

ASSUNTO(S)

matrizes laser ativas single crystals crescimento de cristais micro-pulling-down crystal fibers monocristais crystal growth fibras cristalinas micro-pulling-down fluorides laser hosts fluoretos

ACESSO AO ARTIGO

Documentos Relacionados