Thermal, defects, mechanical and spectral properties of Nd-doped GdNbO4 laser crystal

Abstract

A Nd-doped GdNbO4 crystal was grown successfully by Czochralski method. Its monoclinic structure was determined by X-ray diffraction; the unit-cell parameters are a = 5.38 A, b = 11.09 A, c = 5.11 A, and β = 94.56°. The morphological defects of Nd:GdNbO4 crystal were investigated using the chemical etching with the phosphoric acid etchant. For a new crystal, the physical properties are of great importance. The hardness and density of Nd:GdNbO4 were investigated first. Thermal properties of Nd:GdNbO4, including thermal expansion coefficient and specific heat, were measured along a-, b-, and c-crystalline axes. Thermal properties indicate that the Nd:GdNbO4 pumped along c-axis can reduce the thermal lensing effect effectively. The specific heat is 0.53 J g−1 K−1 at 300 K, indicating a relatively high damage threshold of Nd:GdNbO4. The transmission and emission spectrum of Nd:GdNbO4 were measured, and the absorption peaks were assigned. The strongest emission peak of Nd:GdNbO4 is located at 1065.3 nm in the spectral range of 850–1420 nm excited by 808 nm laser. The refractive index of Nd:GdNbO4 was calculated with the transmission spectrum and fitted with Sellmeier equation. All these obtained results is of great significance for the further research of Nd:GdNbO4.