Study On Growth And Properties Of (Nd,Yb):NYGW Crystals

In recent years,the all-solid-state laser pumped by the laser diode（LD）has become one of the most promising research directions in the laser field,and because of its stable output power and high efficiency,it has gradually become an ideal new coherent light source.The laser working substance is the core of the solid-state laser.Exploring the laser working substance suitable for LD pumping is the key to improving the efficiency of laser.Na Gd（WO₄）₂（NGW）is a typical laser crystal material,especially the rare earth doped NGW crystals,which has a wide absorption peak,low threshold and long fluorescence lifetime,which can be used to achieve full solidification and miniaturization of lasers.In this study,some Gd³⁺ions in the NGW matrix were replaced by Y³⁺ions to form NYGW mixed crystals,which improved the disorder of the NGW crystals and widened the absorption and emission spectrum lines of rare earth ions due to the non-uniform broadening effect.Mixed crystals also increase the specific heat capacity of single crystals.These properties will improve the utilization of the laser pump light and thus improve the efficiency of the laser.In this paper,Nd:NYGW and Yb:NYGW crystals are taken as the research object,the growth technology and spectral properties of the crystals are studied in detail,and the laser properties of the crystals are predicted by spectral parameters.The main research contents are as follows:（1）The high purity NYGW polycrystalline materials were synthesized by high temperature solid phase method and hydrothermal method respectively.The purity and properties of the polycrystalline materials synthesized by the two methods were compared,and the best synthesis process and purification technology of polycrystalline materials were obtained.（2）The growth principle and technology of NYGW crystal are studied,and the factors affecting crystal quality are discussed systematically.NYGW crystals with high purity Na₂CO₃,WO₃,Y₂O₃ and Gd₂O₃ were successfully grown by pulling method.The results show that the structure of NYGW crystals is consistent with that of NGW crystals(space group I_41/a)without phase transition.（3）NYGW crystals doped with different concentrations of Nd³⁺ions were successfully grown by lifting method.XRD shows that Nd:NYGW crystal still belongs to tetragonal phase structure.The absorption spectra of Nd:NYGW crystals are analyzed and the J-O intensity parameters are calculated by the J-O theory.The NIR emission spectra of Nd:NYGW crystal excited at 808 nm are measured,and the absorption and emission cross sections of Nd:NYGW crystal are calculated.The maximum absorption cross section at 808nm is 2.34×10^-20 cm²,and the maximum emission cross section at 1064 nm is 6.68×10^-20 cm².Nd:NYGW crystals have larger emission cross section,which is more conducive to realizing laser output.（4）NYGW crystals doped with different concentrations of Yb³⁺ions were successfully grown by lifting method.The phase structure showed that the doping with Yb³⁺ions did not change the tetragonal phase structure of the NYGW crystal.The absorption peak of Yb:NYGW crystal is located at 976 nm,and the maximum absorption cross section of Yb:NYGW crystal is 2.06×10^-20 cm².The emission band of Yb:NYGW crystal is located at 980nm-1100 nm,and the maximum emission cross section of Yb:NYGW crystal is calculated to be 1.66×10^-20 cm².The gain cross section of the crystal is calculated and a lower inversion level implies a lower pumping threshold for the Yb:NYGW crystal.All these results indicate that Yb:NYGW crystals have high application potential in the near infrared field.