| With the rapid development and widespad application of laser technology, the development and application of photoelectric technology mainly conposed of laser tectmology will have become one of the main symbols for a national high-tech. The catalyst driving this photoelectric teclmical revolution is the application of all kinds of lasers. As a result, laser crystal plays a more and more important role as development and industrialization of fundamental materials. The growth of high quality laser crystal is the foundation of high efficiency solid-state laser pumped by laser diode. The characteristics of High peak power, high average power and tunablity of laser pumped by LD will be a developing trend at present and in the future, and furthermore, the advantages of high power, micromation, multiwave and tunablity will also have become a developing trend of laser crystal related to above characteristics.In this paper, the growth and performance of single-doping RE:KY(WO4)2,RE:KGd(WO4)2 (RE are Yb3+, Ho3+, Er3+) and codoping RE:Yb:KY(WO4)2,RE:Yb:KGd(WO4)2 (RE are Tm3+, Nd3+, Er3+) laser crystals have been studied. It is ported that many excellent laser and luminescence materials are composed of compound tungstate of alkali metal and rare earth ions. These compounds can be developed as low threshold value microminiaturized laser pumped by LD, owing to several merits, such as high activating ion-concentration and little quenching of fluorescence etc. KGd(WO4)2 and KY(WO4)2 crystals in the low temperature phase belong to monoclinic system, and partial Gd3+ and Y3+ have been replaced by lanthanide, which have become a more promising laser host materials. Rare earth ions can be used widely as active ions for laser crystals. Especially, researches on Yb3+ as laser active ions have been developing rapidly. Laser output of Yb3+ has been obtained in many host materials of laser crystals. These crystals show excellent laser performance in aspects of continuous wave, wavelength tuning, self-Q-switched, self-double frequency and passive mode-locked et al. Meanwhile, Yb3+ has also been a sort of high efficiency sensitive ion, which can be used as absorption sensitizing agent of many sorts of laser active ions, such as Er3+, Ho3+, Pr3+, Tm3+, Nd3+, Cr4+ and so on.Crystals have been grown by Top Seeded Solvent Growth(TSSG) and Kyropoulos methods, which is the integration between flux and Czochralski methods. If you want to obtainβ-phase crystal used for solid-state laser, crystals must have been grown below phase transformation temperature owing to solid-state phase transformation below phase transformation temperature of KGW and KYW crystals. Compared with performance and growth condition between K2WO4 and K2W2O7,K2W2O7 can be used as flux. The rational temperature field, the method of material preparation and technological parameters have been designed through further explore of more experiments. Finally, high optical quality crystals have been obtained, which contain Yb:KYW, KYbW, Er:KYbW, Er:KGW, Ho:KGW and Er:Yb:KYW, Er:Yb:KGW, Tm:Yb:KYW, Tm:Yb:KGW, Nd:Yb:KYW crystals.Crystal crack, grow strips, grow steps, grow mound and parcel have been analyzed. We got the conclusion that in order to get high quality crystal, we should degrade the fluctuate between temperature, concentration and growing speed.X-ray powder diffraction analysis was given to the crystal powder so as to identify structure of the crystals. The melting point and phase transition were obtained by TG-DTA analysis. The infrared spectrum and Raman spectrum of crystal were measured. The vibration modes was analysed and vibrational frequencies of vibratory activity was assigned. The absorption spectra and fluorescent spectra of crystals were measured. The cross section of main absorption and emission peaks in the crystals were calculated respectively. The structure and performance of Yb:KYW, KYbW, Er:Yb:KYW, Er:Yb:KGW crystals were studied mainly.X-ray powder diffraction analysis has been given to the Yb:KYW crystal. It can be indicated that as-grown crystals are all the crystals of low temperature phase. The cell parameter of them is that a=10.63A, b=10.34A, c=7.55A,β=130.75°, Z=4 or a'=8.07A, b'=10.35A, c'=7.55A,β'=94.34°, Z=4. The melting point and transition temperature were 1045℃and 1010℃by TG-DTA curve, respectively. The infrared spectrum and Raman spectrum of crystal were measured. It is indicated that the vibrational absorption of WO42- group lie in the range of 200～1000nm, and the peak value of vibrational spectra and the vibration of atomic group correspondingly was assigned. The absorption spectra for different thick samples were measured. The absorption linewidth of main peak (981nm) was up to above 8.0nm, and the absorption cross sections of peak value calculated was 1.33×10-19cm2. The fluorescent spectra showed that there were stronger emission peaks near 990nm, 1010nm and 1030nm. The emission linewidth of main peak(1030nm) was up to 16nm, and the stimulated emission cross section calculated was 3.1×10-20cm2. The fluorescent lifetime estimated was 0.56ms, which is close to the actual value(0.60ms). Room temperature CW laser action of Yb:KYW crystal sized 9.5×9.5×1.1mm3 at 1026～1044 nm has been demonstrated under pumping by 980 nm laser diode. A slope efficiency of Yb:KYW laser up to 52% has been obtained.The KYbW crystal was identified asβ-KYbW by XRD analysis. The lattice parameters of KYbW were: a=10.61A, b=10.29A, c=7.49A,β=130.65°and a'=8.07A,b'=10.29A, c'=7.49A, 13'=94.34°calculated by XRD analysis. The melting point and transition temperature were 1058℃and 1031℃by TG-DTA curve, respectively. The absorption spectrum and fluorescence spectrum of KYb W were measured. The absorption cross section at 981nm was calculated as 1.11×10-19cm2, which showed that efficiency coefficient of Yb3+ in KYbW was high. The emission wavelength of fluorescence was 1007nm and 1037nm, and the emission line-width at the chief peak 1037nm run up to 13nm, so KYbW was an excellent gain medium for tunable laser. The emission cross section at 1037nm was calculated as 3.4×10-20cm2.The Er:Yb:KGW crystal was identified asβ-Er:Yb:KYW by XRD analysis. The transition temperature and melting point were 1031℃and 1067℃by TG-DTA curve, respectively. The infrared spectra and Raman spectra were measured, and vibrational frequencies of infrared and raman active modes for Er:Yb:KYW crystal were assigned. Absorption spectrum of the sample was measured, there existed four strong peaks at 380, 525nm, 933nm and 981nm, and the absorption cross section was 3.2×10-20cm2 at main peak 981nm. Fluorescence spectrum of the crystal was measured by excitation source with 488nm and 978nm respectively, and the lifetime of 4I13/2 was 4.8ms, which showed that Yb3+ as sensitization doped in Er:KYW crystal was significance for absorbing pump light and obtaining strong laser of 1540nm.
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