Growth and spectral properties of Tm~(3+)-doped NaGd(WO_4)_2 crystal

摘要

Thulium doped sodium gadolinium tungstate crystals with sizes of about 20 mm x 45 mm were grown successfully by the Czochralski technique along the (001) orientation. X-ray powder diffraction (XRD) of sodium gadolinium tungstate was described and the linear thermal expansion coefficients for the c- and a-axes were measured as 1.60 x 10~(-5) and 7.89 x 10~(-6) ℃~(-1). Polarized absorption spectra, and fluorescence spectra, as well as fluorescence decay curves of Tm~(3+)-doped NaGd(WO_4)_2, have been recorded at room temperature and used to calculate the absorption and stimulated emission cross-sections. Based on the Judd-Ofelt theory, three intensity parameters were obtained. The luminescent quantum efficiency of the ~3H_4 level was determined to be approximately 65% for this material. The emission cross-section of the ~3F_4 → ~3H_6 IR transition at about 1.8 μm was estimated by the reciprocity method.