Laser Crystal Growth And Defects Study Of Yb:KGd(WO₄)₂

Recently, the neodymium-doped crystal Yb3+:KGd(WO), (or Yb:KGW)lasting at 1023-1044nm was demonstrated which exhibits highly efficient free-running operation. The host-crystal structure allows high doping concentration (0.5-10at.%) without considerable concentration quenching. Thus, the specific energy is twice higher than Nd:KGW. The laser crystal also presents other attractive features, such as strong and broad absorption band, makes this laser medium to be an excellent candidate for efficient diode pumping without temperature controlling. The absorption band at 0.981 M m of Yb3+ in the crystal is well matched with the emission wavelength of diode, a solid state laser pump which is very convenient and popular in laser science and technology today.We have compared K2WO4 and K2W2O7, analysed the phase diagram and temperature field in this paper, Yb:KGW crystal was grown by the TSSG slow cooling method from a suitable flux KWO following the steps: homogenized twice, seeking, slow cooling process. The technological parameters: the solution temperature was slowly decreased at0.05 /h ,the growing crystal was rotated at 4rpm for 10 days.By analysis on the X-ray diffraction spectrum of Yb:KGW crystalpowder sample and KGW powder sample, found the same distribution ofthe diffraction maximum and the relative intensity, so we conclude that the - Yb:KGW crystal is of high-temperature phase, monoclinic system, andC2/c space group.On the base of TG-DTA, found the Yb:KGW crystal has very good thermal stability under 1100 , which has two obvious absorption peak at 1088 and 1025 , contrast with the pure KGW crystal ( melting point at 1005 , phase transition temperature from tetragonal system to monoclinic is 1075 ), we know the Yb:KGW crystal's melting point is the absorption peak at 1088 , phase transition peak from tetragonal system to monoclinic is the absorption peak at 1025 .The defects in crystal, including cracking, hillocks, growth fringe, growth steps and inclusions were observed. These defects in crystal can be explained by the instability of the growth and cooling, etc. Another factor is the high viscosity in this system, XRD indicated that most of the inclusion was flux.XPS shows that the crystal has elements W, K, Yb, O, Gd from the data of electron energy level and binding energy.