Acoustic and Optical Properties of Er$^{3+}$- doped LiNbO$_{3}$

Elastic constants of pure and Er$^{3+}$doped lithium niobate (LiNbO$_{3})$ single crystals have been determined using resonant ultrasound spectroscopy (RUS). When comparing the elastic constants for pure and doped LiNbO$_{3}$ crystals, the bulk modulus was found to increase by 5.2{\%} after doping. Also the elastic constants were compared. C$_{11}$ decreased by 4{\%}, C$_{12}$ increased by 18{\%} and C$_{44}$ increased by 16.6{\%}. The surface-doping explains the decrease in elastic constant in only one direction. The presence of Er$^{3+}$ ions on the surface of LINbO$_{3}$ has been monitored using photoacoustic spectroscopy. The photoacoustic spectrum revealed very weak absorptions corresponding to $_{4}$F$^{7/2}$, $_{4}$F$^{9/2 }$and $_{2}$H$^{11/2}$ levels of Erbium, indicating the presence of Erbium.