Emission and absorption cross sections of Er³⁺:LiNbO₃ crystal: Composition effect

We report Er³⁺-doping, Mg²⁺-codoping and crystal composition effects on emission and absorption cross sections of Er³⁺-only doped and Er³⁺/Mg²⁺-codoped LiNbO₃ crystals, in which Er³⁺ concentration ranges from 0.3 to 2.7 mol% and Mg²⁺ concentration from 1.2 to 7.4 mol%. The emission cross section spectra were calculated from the measured fluorescent spectra and the absorption cross section spectra were computed using the McCumber relation. The results show that increasing Er³⁺ concentration tends to decrease the cross section, while codoping with Mg²⁺ or increasing crystal composition tends to increase the cross section. As the composition is close to the stoichiometry, the cross section value tends to a constant. These effects are related to Er3+ site redistribution induced by doping or crystal composition alteration.