## 3 Results and Discussion
\begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \multirow{2}{*}{**Measurement**} & \multicolumn{6}{c}{**Dy3+ Doped Concentration, mol\%**} \\ \cline{2-7}  & **0.0** & **0.2** & **0.4** & **0.6** & **0.8** & **1.0** \\ \hline Refractive index (\(n\)) & 2.295 & 2.305 & 2.317 & 2.331 & 2.344 & 2.355 \\ Reflection loss (R\({}_{\rm L}\)) & 0.154 & 0.155 & 0.157 & 0.159 & 0.161 & 0.163 \\ Molar refraction (R\({}_{\rm m}\)) (cm\({}^{-3}\)) & 5.741 & 4.330 & 4.355 & 4.366 & 4.375 & 4.393 \\ Oxygen packing density (OPD) & 86.57 & 86.46 & 86.44 & 86.72 & 87.01 & 87.81 \\ Optical basicity (\(\Lambda\)) & 1.240 & 1.248 & 1.257 & 1.268 & 1.277 & 1.285 \\ Optical electronegativity (\(\chi\)) & 0.919 & 0.903 & 0.885 & 0.863 & 0.845 & 0.829 \\ Metallisation criterion (M) & 0.412 & 0.410 & 0.407 & 0.403 & 0.400 & 0.397 \\ Molar refractivity (R\({}_{\rm M}\)) (cm\({}^{-3}\)) & 17.227 & 17.324 & 17.420 & 17.467 & 17.505 & 17.576 \\ Molar polarizability (\(\alpha_{m}\)) \(\times 10^{-24}\) (cm\({}^{-3}\)) & 2.275 & 1.716 & 1.716 & 1.730 & 1.734 & 1.741 \\ Dielectric constant (\(\varepsilon\)) & 5.267 & 5.313 & 5.368 & 5.433 & 5.494 & 5.546 \\ Optical dielectric constant & 4.267 & 4.313 & 4.368 & 4.433 & 4.494 & 4.546 \\ Electron polarizability (\(\alpha_{o}\)) & 2.672 & 2.687 & 2.703 & 2.723 & 2.739 & 2.753 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Optical properties of prepared glass samples. Figure 9: Variation in metallisation criterion with mol% Dy\({}_{2}\)O\({}_{3}\). The PL spectra for the current samples of various Dy\({}^{3+}\)-doped compositions of (LAB) glass registered at room temperature in the wavelength region 420-720 nm below the excitation of the wavelength 375 nm are exhibited in Figure 10.  
It was noticed that the emission peaks' intensity increased gradually as Dy\({}^{3+}\) concentrations increased from 0.2 mol\(\%\) to 1 mol\(\%\). The bands obtained in this present work are in agreement with the previous investigations [39]. Five emission peaks were spotted, containing two comparatively intense emission bands at nearly 481 and 575 nm, respectively, for the transitions \({}^{4}\)F\({}_{9/2}\rightarrow\)\({}^{6}\)H\({}_{15/2}\) and \({}^{4}\)F\({}_{9/2}\rightarrow\)\({}^{6}\)H\({}_{13/2}\), and three considerably feeble bands at almost 458, 661 and 689 nm corresponding to the transitions \({}^{4}\)I\({}_{15/2}\rightarrow\)\({}^{6}\)H\({}_{15/2}\), \({}^{4}\)F\({}_{9/2}\rightarrow\)\({}^{6}\)H\({}_{11/2}\) and \({}^{4}\)F\({}_{9/2}\rightarrow\)\({}^{6}\)H\({}_{9/2}\), respectively [40]. These transitions are similar to other study, where the transition \({}^{4}\)I\({}_{15/2}\) level excites the Dy\({}^{3+}\) ions at band 458 nm [12]. The excited Dy\({}^{3+}\) ions populate the \({}^{4}\)F\({}_{9/2}\) meta-stable state during rapid of non-radiative decay process due to the small energy gap between 4I\({}_{15/2}\) and \({}^{4}\)F\({}_{9/2}\) states [41]. The main higher band at 575 nm (\({}^{4}\)F\({}_{9/2}\rightarrow\)\({}^{6}\)H\({}_{13/2}\)) in the yellow range of the visible spectrum is a supersensitive transition following the selection rules (\(\Delta\)J = \(\pm\)2 and \(\Delta\)L = \(\pm\)2) [42]. In addition, the band at 481 nm (\({}^{4}\)F\({}_{9/2}\rightarrow\)\({}^{6}\)H\({}_{11/2}\)), which is in the blue range, has low sensitivity to the host glass and is lower than the band at 575 nm that applies the selection rules (\(\Delta\)J = \(\pm\)3). Therefore, the intensity of this transition is heavily impacted by the surrounding environment. Further to this, the weak intensity of emission bands appears at 661 nm (\({}^{4}\)F\({}_{9/2}\rightarrow\)\({}^{6}\)H\({}_{11/2}\)) and 689 nm (\({}^{4}\)F\({}_{9/2}\rightarrow\)\({}^{6}\)H\({}_{9/2}\)) is in the red range, which follows the selection rules (\(\Delta\)J = \(\pm\)1) and (\(\Delta\)J = 0), \({}^{6}\)F\({}_{11/2}\), respectively [33; 43].