## 3 Results
### Absorption and Emission Properties  
The room temperature absorption spectra were obtained for both samples in the 300-1700 nm range. As an example, Figure 1 shows the absorption spectra as a function of the wavelength for the sample doped with a 4 wt% of Er\({}_{2}\)O\({}_{3}\). The spectrum consists of 10 absorption bands corresponding to the transition from the \({}^{4}\)I\({}_{15/2}\) ground state to the \({}^{4}\)G\({}_{11/2}\), \({}^{2}\)H\({}_{9/2}\), \({}^{4}\)F\({}_{3/25/2}\), \({}^{4}\)F\({}_{7/2}\), \({}^{2}\)H\({}_{11/2}\), \({}^{4}\)S\({}_{3/2}\), \({}^{4}\)F\({}_{9/2}\), \({}^{4}\)I\({}_{19/2}\), \({}^{4}\)I\({}_{11/2}\), and \({}^{4}\)I\({}_{13/2}\) of Er\({}^{3+}\) excited states ions [1]. Visible emission spectra were obtained at room temperature under excitation of the \({}^{4}\)F\({}_{7/2}\) level at 488 nm. Multiphonon relaxation processes populated the lower levels resulting in the emission bands observed at around 530, 548, and 660 nm which corresponded to transitions from the \({}^{2}\)H\({}_{11/2}\), \({}^{4}\)S\({}_{3/2}\), and \({}^{4}\)F\({}_{9/2}\) levels to the ground state. Figure 2 shows the emission spectra of both glasses. The main emission corresponded to the \((^{2}\)H\({}_{11/2}\), \({}^{4}\)S\({}_{3/2}\))\(\rightarrow\)\({}^{4}\)I\({}_{15/2}\) transition. A weak red emission was also observed from the \({}^{4}\)F\({}_{9/2}\) level. This level was populated through multiphonon relaxation processes from the \({}^{4}\)S\({}_{3/2}\) level. The experimental decays of the luminescence from \({}^{4}\)S\({}_{3/2}\) and \({}^{4}\)F\({}_{9/2}\) levels were obtained at room temperature for both glasses under excitation at 488 nm. Table 2 shows the values obtained by a fit to a single exponential function. It can be observed that lifetimes of these levels were found to be similar for both glasses, with values slightly higher for the glass doped with a 1 wt% of Er\({}_{2}\)O\({}_{3}\). As an example, Figure 3 shows the experimental decays from the \({}^{4}\)S\({}_{3/2}\) and \({}^{4}\)F\({}_{9/2}\) levels under excitation at 488 nm for the sample doped with 1 wt%. Lifetime was also measured at room temperature for the \({}^{4}\)I\({}_{13/2}\) level under excitation at 800 nm corresponding to the level \({}^{4}\)I\({}_{9/2}\). It was also found that lifetime was slightly higher for the glass doped with a 1 wt% of Er\({}_{2}\)O\({}_{3}\). The decay from the \({}^{4}\)I\({}_{13/2}\) level was found to behave like a perfect single exponential, whereas decays from \({}^{4}\)S\({}_{3/2}\) and \({}^{4}\)F\({}_{9/2}\) excited levels slightly deviated from a perfect exponential behavior. The observed lifetimes were in the same order of magnitude than those reported for other silicate and aluminosilicate glasses [10; 11; 32]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Na** & **Mg** & **Al** & **Si** & **Ti** & **Zr** & **Er** \\ \hline Er1 & 0.70 & 1.81 & 28.11 & 65.99 & 2.00 & 0.98 & 0.41 \\ Er4 & 0.86 & 1.75 & 28.12 & 65.11 & 1.84 & 0.89 & 1.43 \\ \hline \end{tabular}
\end{table} 
Table 1: Compositional analysis in at% of the Er-doped samples manufactured in an oxygen atmosphere. Figure 1: Room temperature absorption spectrum of Er\({}^{3+}\) in the aluminosilicate glass doped with 4 wt% Er\({}_{2}\)O\({}_{3}\). The fluorescence spectra at room temperature corresponding to the \({}^{4}\)I\({}_{13/2}\)\(\rightarrow\)\({}^{4}\)I\({}_{15/2}\) transition were measured by exciting the samples at 802 nm. As shown in Figure 4 both samples presented a maximum at around 1528 nm. Effective bandwidth (\(\Delta\lambda_{\textit{eff}}\)) was measured according to  
\[\Delta\lambda_{\textit{eff}}=\int\frac{I(\lambda)d\lambda}{I_{max}}, \tag{1}\]  
where \(I(\lambda)\) is the intensity of the emission spectrum as a function of the wavelength and \(I_{max}\) is the peak intensity. It was found that the effective bandwidth increased from 62.5 nm for the sample doped with 1 wt% to 66.3 nm for the sample doped with 4 wt% of Er\({}_{2}\)O\({}_{3}\).