Photothermal measurement with mirage effect for investigation of LiNbO₃ single crystals

Abstract
Results of measurements of the thermal diffusivity of pure and doped lithium niobate single crystals are presented. A reference sample was a pure crystal. The others were doped with: Cu (0.05%at.), Dy (0.1%at., 1.0%at., and 1.7%at.), and Er + Yb (1.0%at. Er + 1.0%at. Yb) ions. Thermal properties were determined in [100], [120] and [001] crystallographic directions. Experimental studies were carried out using photothermal method based on mirage effect. This method based on determination of a phase lag connected with propagation of a thermal wave in investigated sample. Obtained results showed considerable anisotropy of the thermal diffusivity of pure crystal and doped samples. The thermal properties in [001] direction (c-axis) is higher than in directions perpendicular to it. Unexpectedly, anisotropy of the thermal diffusivity in plane (001) was also observed.