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| Author(s): |
Dione Fagundes de Sousa
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT) |
| Defense date: | 2000-11-24 |
| Examining board members: |
Luiz Antonio de Oliveira Nunes;
Vanderlei Salvador Bagnato;
Francisco Eduardo Gontijo Guimarães;
Younes Messaddeq;
Sidney José Lima Ribeiro
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| Advisor: | Luiz Antonio de Oliveira Nunes |
| Abstract | |
In this work two vitreous compositions were studied, that are: fluoroindogalate (30PbF2 - 15InF3 - 20GaF3 - 15ZnF2 - 20CaF22) and LSCA (41,5Al2O3 - 47,4CaO - 7SiO2 - 4,1MgO) - Low Silica Content Calcium Aluminates. The fluoroindogalate host was doped with two sets of rare earth ions: Tm3+ + Ho3+ and Er3++Yb3+, whereas the LSCA host was only doped with Er3+ and Yb3+ ions. The aim of the work was the characterization of these hosts as possible active media for solid state lasers in the spectral regions of 2,0 µm (Ho3+) and 2,8µm (Er3+). In this sense, optical absorption, photoluminescence and lifetime experiments were performed. From the resulting data, Judd-Ofelt intensity parameters, energy transfer microparameters and the electronic transitions 5I7→ 5I8 (Ho3+) and 4I11/2→ 4I13/2 (Er3+) optical gain coefficients were calculated. This work\'s contribution to the rare earth spectroscopy lies in the characterization of such ions in terms of the energy transfer parameters using the Dexter, and Yokota and Tanimoto models considering that these data are not available in the specialized literature. The results have shown that higher than dipole-dipole order processes occur in the interactions Tm3+→ Tm3+ and Tm3+→ Ho3+. The Ho3+ 5I7→ 5I8 transition presents positive optical gain coefficient starting from the excitation density of 1.2 kW/cm2. The energy transfer processes Er3+→ Er3+ and Er3+→ Yb3+ occur via dipole-dipole mechanism and the Er3+ 4I11/2→ 4I13/2 transition is not auto terminated in the fluoroindogalate host. The optical gain coefficient for this transition is always positive for any excitation density. The LSCA host presents auto termination of the Er3+ 4I11/2→ 4I13/2 making it necessary the insertion of upconversion mechanisms for the observation of the optical gain in this electronic transition (AU) | |