Study On The Defect Structure And Optical Properties Of Sc:Yb:Nd:LiNbO₃ Crystal With Different Sc³⁺ Dopant Concentrations

In this study,a series of Sc:Yb:Nd:Li Nb O₃crystals with the same doping concentration of Yb³⁺（1mol%）and Nd³⁺（1mol%）ions and different doping concentration of Sc³⁺（0,0.5,1,1.5 mol%）were grown by the Czochralski method.Sc:Yb:Nd:Li Nb O₃crystals with no internal and surface cracks,high transparency and optical homogeneity are prepared to test samples through processes such as polarization,cutting,grinding,and polishing.The crystals were processed into wafer samples labeled Sc Yb Nd-0,Sc Yb Nd-1,Sc Yb Nd-2 and Sc Yb Nd-3 for various performance tests.The effective segregation coefficient of each doped ion of Sc:Yb:Nd:Li Nb O₃crystal is obtained through inductively coupled plasma mass spectrometry（ICP-AES）test.As the doping concentration of Sc³⁺ions increases,the effective segregation coefficient of Yb³⁺and Nd³⁺ions decrease.Through X-ray diffraction test,it is confirmed that the structure of the lattice has no variation due to the doping of Sc³⁺ions.Sc³⁺ions enter the crystal by replacing the ions at normal lattice points.The transformation law of defect structure in Sc:Yb:Nd:Li Nb O₃crystal lattice can be reflected by the variation of lattice constant.Combined with in IR transmission spectroscopy and UV-VIS-NIR spectroscopy test results,analyzed the doping ion occupancy mechanism and crystal defect structure changes.When the concentration of Sc³⁺ions doped into the crystal is smaller than the content of intrinsic defects in the Yb:Nd:Li Nb O₃crystal,Sc³⁺ions preferentially occupy the positions of intrinsic defects anti-niobiumNb_Li^4（10）and lithium vacanciesV^-_Li and to formSc_Li^2（10）defect structures.The doping concentration of Sc³⁺ions in the melt used for crystal growth reached 1mol%,theNb_Li^4（10）defects in the crystal lattice are completely replaced proved that the Sc³⁺ions reached the threshold concentration.Continue to increase the Sc³⁺ion doping concentration,Sc³⁺ions will replace the Li and Nb sites in the normal crystal lattice to formSc_Li^2（10）-Sc_Nb^2-structure,which is the charge self-compensates for the defect group.The optical damage resistance ability of Sc:Yb:Nd:Li Nb O₃crystal is measured by the light scattering threshold energy flux method.The results can prove that Sc³⁺is an effective optical damage resistance ion,even with a lower doping concentration,the exposure energy threshold of Sc:Yb:Nd:Li Nb O₃crystal can be increased by 5 times.An increase in the exposure energy threshold represents an increase in the resistance of the crystal to light damage.The exposure threshold energy of Sc（1.5mol%）:Yb（1mol%）:Nd（1mol%）:Li Nb O₃sample reaches751.72J/cm~2,which is about 210 times that of the undoped Sc³⁺ion sample,and it is the crystal with the strongest light damage resistance ability in this experiment.