Complete sets of elastic constants and photoelastic coefficients of pure and MgO-doped lithium niobate crystals at room temperature

This paper presents the results of ultrasonic measurements of $LiNbO3$ and $LiNbO3:MgO$ crystals. The tensors of piezoelectric coefficients, elastic stiffness constants, and elastic compliances are determined for both crystals at room temperature. Combining these data with the results of piezo-optical measurements, a complete set of photoelastic tensor coefficients is also calculated. Doping of $LiNbO3$ crystals by MgO does not lead to a considerable modification of their elastic and photoelastic properties. However, $LiNbO3:MgO$ is characterized by a considerably higher resistance with respect to powerful light radiation, making it promising for future application in acousto-optic devices that deal with superpowerful laser radiation. Presented here are the complete tensor sets of elastic constants and photoelastic coefficients of $LiNbO3$ and $LiNbO3:MgO$ crystals that may be used for a geometry optimization of acousto-optical interaction providing the best diffraction efficiency of acousto-optical cells made of these materials.