Ytterbium-doped YPO₄ Crystal Growth, Spectroscopy And Laser Performance Research

The vanadate crystals have been studied extensively as laser materials,in particular for the Nd ion doped vanadate crystals,having a series of advantageous laser properties,these phosphate crystals possess the same structures with vanadate crystals,also have obtained more and more attentions.The main objective of this work is to explore the Yb:YPO₄ crystal,including the growth of different concentrations Yb ion doped YPO₄crystals,characterization,analysis of spectral properties,and measurement of laser properties.Different concentrations single crystals of Yb:YPO₄ were grown by Flux method with Pb₂P₂O₇ flux,we have discussed the Macro-defects of Yb:YPO₄ crystals,such as inclusions,cracking and so on.We have directed the 5 at.%Yb:YPO₄ crystal and drawn the crystal ideal shape.The 5 at.%Yb:YPO₄ crystal structure was analyzed by X-ray single crystal diffractometer,which indicated that this crystal belongs to tetragonal crystal system and its space group is I4₁/amd.The single Yb:YPO₄ crystal was measured by X-ray powder diffractometer,we have contrasted and analysised of XRD spectra of crystals with different concentrations,we found that the high concentration of doping does not cause the change of crystal structure,and the cell parameters were calculated,it is found that the dates obtained from the single crystal diffraction are the same basically.Compared with pure YPO₄ and YbPO₄ crystals,it is found that Yb³⁺was successfully doped into the YPO₄ crystal.The polarized absorption spectra were determined at room temperature by use of a plate-shaped 5 at.%Yb:YPO₄ crystal of 1.8 mm in thickness,polarized absorption cross-section were calculated.The polarized emission cross-section were calculated by use of the integral method of reciprocity,the main spectroscopic parameters of the Yb:YPO₄ and Yb:LuPO₄ crystals were compared.For the first time,efficient continuous-wave laser action of the 5 at.%Yb:YPO₄ crystal was achieved employing the simple plano-concave resonator,with output coupling changed in a wide range of 0.5%-40%,the maximum output power of 3.62 W in the case of T=5%,corresponding to the slope efficiency of 38%,with an optical-to-optical efficiency of 36%,the laser action of the 10 at.%Yb:YPO₄ and 15 at.%Yb:YPO₄ were achieved.