Estudo de sistemas vítreos dopados com Er3+ visando aplicações em fibras e amplificadores ópticos

Abstract

In this work we have studied the thermal and optical properties of glassy systems PAN (P205 - Al2O3 - Na2O), PANK (P2O5 - Al2O3 - Na2O - K2O), PANB (P2O5 - Al2O3 - Na2O - BaO), e SNAB (SiO2 - Na2O - Al2O3 - B2O3) [mol%], undoped and doped with increasing concentrations of xEr2O3, aimed at applications in optical fibers and optical amplifiers. The choice of the host medium is critical, as this influences the spectroscopic parameters of rare earth ions (TR) inserted in the material. This study was divided into two stages. The first thermal properties were determined by Differential Thermal Analysis (DTA), optical optical absorption (OA) and Raman spectroscopy (RE), and the refractive index (n) of undoped glass matrix. In the second step, the glass matrices were doped with Er2O3 increasing concentrations (wt%) in order optical amplification around 1534 nm which corresponds to the third optical window (spectral region where optical fibers present the lowest attenuation). These doped glass matrices were characterized by Optical Absorption (OA), photoluminescence (PL) and photoluminescence of Temporal Resolution (PLRT) as well as the determination of the refractive index (n), density (ρA) and concentration (N). From these results, we used the Judd-Ofelt theory to determine the spectroscopic parameters of Er3+ in these systems glassy inserted. The results obtained in the first step showed that the glass matrix PANK had good thermal properties, relatively high refractive index, and good optical properties, such as lower density hydroxyl (OH-) in relation to the other glass matrices and transparency in the spectral region corresponding to the optical windows. In the second stage, it was observed from the PL spectra, an increase in width at half maximum of the emission band related to the transition 4I13/2 → 4I15/2 of Er3+ ions as a function of ion concentration Er2O3. The lifetimes of the state 4I13/2 of Er3+ to all of the arrays decreased with increasing concentration of Er3+, giving evidence of the presence of cases non-radioactive as: (i) cross relaxation (CR) (ii) migration energy (ME) and (iii) high energy phonons network. The spectra of the glass matrices showed that the hydroxyl group density did not change significantly with increasing concentration of Er3+. Raman spectra proved that the relaxation process is favorable for multifônons all glass matrix as the energy difference on the transition 4I13/2 → 4I15/2 (6519 cm -1) Er3+ ion corresponds to a multiple of their modes vibrational, since the glass to the base of P2O5 5 phonons are required for the relaxation process occurs multifônons and the glass matrix SNAB, 6 phonons are required. From the model STOKOWSKI (1993) found that the process of cross relaxation (CR) is not a dominant process. In addition to this, the processes of energy migration (EM) and phonon energy of the network is also responsible for the decrease in the lifetime of the excited state 4I13/2 of Er3+ ion. The longer lifetime of this state was 8.75 ms and quantum efficiency η = 88%, related to the vitreous matrix PANK Er2O3 + 0.2(wt%). This vitreous matrix and presents good thermal and optical properties, showed the highest experimental lifetimes (ζexp) and quantum efficiency (η) compared to other Matrices. Therefore, the glass matrix is PANK great promise for use in optical amplifiers.