| Generally,there are two methods to investigate new laser lights,one is to explore new laser materials,and the other is to convert the frequency of the laser lights that is known.In recent years,much attention has been paid to the designing and operation of all-solid-state Raman lasers based on the stimulated Raman Scattering(SRS)of crystals.Raman-aetive crystal is the hardcore part of the Raman laser.Thereby,reliable and efficient Raman-active crystals with high quality become a hotpot in the field of materials.KGd(WO4)2(KGW)and KY(WO4)2(KYW)crystals are the most frequently used Raman-active crystals,especially the Nd:KGW crystals.A stoke output of 800m W has been operated using Nd:KGW crystals through self-Raman scattering by H.M.Pask.Crystalline KGW belongs to monoclinic system,space group C2/c.Many new characteristics in their performance are found due to their strong anisotropy structure.It has been proposed to be an ideal laser crystal with excellent properties of laser,stability of physics and chemistry.Crystalline KLuW belongs to the system of KGW group,they have the similar structure and other properties.It is important to study the growth and performance characteristic of KLuW system,the primary coverage is as fellows:1.The growth of monoclinic tungstates:Many high quality and large size crystals have been grown including KLuW,KYbW,Nd:KLuW,Tb:KLuW and Yb,Tm: KLuW crystals.All of them were grown along c-axis directions using the top-seeded solution growth method.They can be cut into samples with enough size using in the SRS experiments.The growth of tetragonal tungstates:Crystalline NaLuW,NaYbW and NaTmW has been grown.They are large enough to test their basic optical and thermal properties. Additionally,some new crystals have also been grown,such as crystalline KxNa1-xLuW and KLuxGd1-xW. 2.The investigation of basic properties,such as density,refractive index, element analysis and defects.The density of crystalline KYbW was measured using the buoyancy method at room temperature and its value is 7.56 g·cm-3which is a little smaller than the theory value of 7.61g·cm-3.The refractive indexes were measured by prism coupling method at 632.8 nm and 1539 nm.The optic axial angle V was calculated to be less than 45°,so crystalline KLuW is positive biaxial crystal.Because the different properties should be investigated in different systems of coordinates,we explain the five coordinates in detail.3.The investigation of the structure and phase transiton using the high temperature X-ray diffraction method,DTA and TG methods.There are two obvious change,one(1000℃—1100℃)is because of the melt of the crystal,the other(800℃—900℃)is because of the phase transiton below the melt point.There are also two endothermal peaks,corresponding to the melting peak,s(1000℃—1100℃)and the phase transition peaks(800℃—900℃).They are anastomonic,which indicate that crystalline KLuW and Nd:NaLuW have phase transition below the melt point.4.The investigation of thermal properties including DTA,TG,specific heat, thermal expansion coefficient,density changing along the temperature,thermal diffusion coefficent and thermal conducitvity.The density changed from 7.555g/cm3 to 7.463 g/cm3.The thermal diffusion coefficient and thermal conductivity indicate the large anisotropy.5.The absorption and luminescence spectra of Nd3+doped crystals have been measured.The main spectra paremeters have been calculated using J-O theory and the laser performance has been assessed.Additionally,various rare earth ions doped KLuW have been investigated.6.The space group theoretical analysis and assignment of the lattice vibration modes of crystalline Nd:KLuW with various geometries have been performed.The lattice vibration spectra were mainly arised from internal vibrations of the WO6 cluster. The X(ZZ)(?)configuration was analysed in detail.Two higher lattice vibration frequency are observed at 761cm-1and 91 cm-1,the half line width is 15.6 cm-1和10.4 cm-1,correspinding to the relaxation time of 0.68ps and 1.02ps,respectively.The results indicate that the crystal is appreciable in the ps or fs pulse lasers.7.The stimulated Raman scattering of crystalline KLuW was studied.The direction is selecte along the b and c axis,corresponding to the physical coordinates of Y and Z axis.The conversion efficients are 16.42%and 7.77%,the pulse width is 8.309ns and 27.41 ns respectively.8.Continuous wave(CW)laser output of Nd3+doped tungstates was studied.The properties ofNd:KLuW is more excellent than other tungstates.
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