Optical properties and laser performance of neodymium doped scheelites CaWO4 and NaGd(WO4)2

Nd-doped CaWO₄ (CWO) and NaGd(WO₄)₂ (NGWO) single crystals with good optical quality have been grown by the Czochralski technique. The neodymium distribution coefficient in these matrices is about 0.4 for CWO and close to unity for NGWO. Polarized absorption and emission spectra have been recorded at room temperature and used to calculate the absorption and stimulated emission cross-sections.1 and 2% Nd : CWO and 1 % Nd:NGWO laser rods have been tested in a cavity longitudinaly pumped by an 1 W AIGaAs laser diode and compared to Nd : YAG and Nd:YVO₄ rods in the same conditions. The 2% Nd: CWO rod exhibits the best performance with slope efficiencies of 64%, higher than in the case of YAG and equal to the YVO₄ samples. The dependence of the laser output power versus the diode temperature has been measured for all these materials. The laser output of Nd: CWO was found to be nearly as stable as for Nd : YVO₄ and much more stable than in the case of Nd : YAG. A CWO microchip has also been tested for the first time to our knowledge.