Investigation On The Correlation Among Composition, Structure And Property Of Yb～(3+) Doped Laser Glasses

The diode Pump Solid State Laser is a new kind of fast developinglaser. In order to meet the requirement of the solid state laser, the researchof laser metatials as working media of the laser has become a majoraspect. Because the configuration of Yb³⁺ ions is very simple withoutcross relaxation and excited state absorption in the theory and theemission spectrum of Yb³⁺ions with main absorption peak around 970nm can be coupled effectively with the wavelength (900～1100nm)pumped by InGaAs laser diode(LD), it is very suitable to be used asexciting particle in the laser materials for using as high-power laser.Recently, Yb³⁺ doped laser glass have been attrcting increasing attentionbecause of its many advantages such as simple preparation technology,easy to form large size and optimizable properties by adjustingcomposition of glass, and have widely been applied in modern industry,medicine, scientific research and military affairs. As having largeemission cross-section and long fluorescence lifetime, the phosphateglasses have been using as major host materials doped-Yb³⁺. However,there is a double bond P=O in the structural unit [PO₄], which results inthe formation of the chain or layer-like structure in the phosphate glass. Itis very clear that the glass with this kind of structure has poorthermo-mechanical property and less practical application.In this article, Yb³⁺ doped phosphate, fluorophosphate andborophophate system laser glasses have been prepared by means ofconventional melt quenching technology. Correlation among composition,structure and properties of three system glasses were investigated byusing of IR, Raman, X-ray diffraction, absorption and emission spectra.The effect of addition of Al₂O₃, B₂O₃ and fluoride on structure andproperties of the phosphate glass was explored, and the change regularitybetween the thermal-mechanical/spectroscopic properties and thealkali/alkaline oxides was found. The structural model of B₂O₃-P₂O₅-ZnOsystem glass was put forward on the basis of the quantitative analysis ofthe glass structure. The properties of three system laser glasses weresystematically compared. It was easy to know that the prepared laser glasses possess the same excellent comprehensive properties as Qx/Yb orFP glass. The main research results were as follows:1) The thermo-mechanical properties of P₂O₅-Al₂O₃-(Nb₂O₅+La₂O₃+B₂O₃)-K₂O-BaO-Yb₂O₃ glasses can be improved by theintroducting appropriate content Ai₂O₃ and the optimum value of Al₂O₃ isabout 7molï¼…. The nonlinear refractive index n₂ decreases but the gaincoefficient increases with increasing Al₂O₃ content from 7molï¼…to13molï¼….2) In P₂O₅-Al₂O₃-(Nb₃O₅+La₂O₃+B₃O₃)-R₂O/MO-Yb₂O₃ systemglasses (R for Li, Na and K, M for Mg,Ca,Sr,Ba and Zn), with increaseof cation field strength Z/r², the thermo-mechanical properties becomebetter in the order of K⁺＜Na⁺＜Li⁺ and Ba²⁺＜Sr²⁺＜Ca²⁺＜Zn²⁺＜Mg²⁺,whereas the glasses containing K₂O and BaO with smaller field strengthshow excellent spectroscopic and laser properties.3) In multicomponent fluorophosphate glasses, the thermo-mechanical properties are improved, at the same time, the nonlinearrefractive index n₂, integral absorption cross-section∑_abs, emissioncross-sectionσ_emi and gain coefficientσ_emi·σ_m increase when Li₂O andBaO are substituted by LiF and CaF₂. In addition, the species and thecontent of fluoride also influence the properties of fluorophosphateglasses, the thermo-mechanical properties are better for thefluorophosphate glasses containing alkali/alkaline fluorides with largercation field strength Z/r², and compared with the fluorophosphate glasseswith low fluoride content, the glasses with high fluoride content showlarger integral absorption cross-section∑_abs and emission cross-sectionσ_emi, but the species of fluoride has little influence on the spectroscopicproperties.4) The devitrifing phenomenon will happen in P₂O₅-B₂O₃-(Nb₂O₅+Al₂O₃)-(K₃O+BaO)-Yb₂O₃ system glasses when B/(B+P) valueis larger than 0.33. However, the phenomenon will not happen in theB₃O₃-P₂O₅-ZnO glasses when B/(B+P) value is larger than 0.4, which isdue to introducting ZnO, which broaden the range of formation ofB₂O₃-P₂O₅-ZnO glasses because of the special coodination of Zn²⁺ ions inthe borophosphate glass. In addition, in the xB₂O₃-(60-X)P₃O₅-40ZnO (x=5, 10, 15, 20 and 25 molï¼…) glass, B³⁺ prefers to form [BO₄] whichstrengthen network structure, whereas Zn²⁺ depolymerizes networkstructure as modifier when x≤20molï¼…. When B₂O₃ content is larger than20molï¼…, the redundant B³⁺ ions form [BO₃] because [BO₄] tetrahedrawith negative charge can not link each other, and Zn²⁺ions form [ZnO₆]in the rich B₂O₃.5) Due to the formation of P-O-B(4) bonds in borophosphate glass,the thermo-mechanical properties are improved greatly and almost areequal to those of silicate glasses. There are various structural units such as[BO₃], [BO₄], [PO₄] etc, therefore the site environment around Yb³⁺become complicated, In xB₂O₃-(60-x)P₂O₅-40ZnO glasses, the integralabsorption cross-section∑_abs increases with increase of B₂O₃ content, butthe emission cross-sectionσ_emi has maximum value of 0.816 pm² atx=15molï¼…, therefore the glass has maximal gain coefficientσ_emi·τ_m.6) It is found that the thermo-mechanical properties become better inthe order of phosphate＜fluorophosphate＜borophosphate glass, wherasthe nonlinear refractive indexes n2 decrease in the order of phosphate＞fluorophosphate＞borophosphate glass. Among the three system glasses,the fluorophosphate glasses have the largest integral absorptioncross-section∑_abs, emission cross-sectionσ_emi and gain coefficientσ_emi·τ_m.Compared with QX/Yb and FP laser glasses, the comprehensiveproperties of the fluorophosphate glassâ…¢-2 and the borophosphate glassBPZ3 are superior to FP, and are equal to those of QX/Yb. The two kindsof glass could be used as the promising working media for diode PumpSolid State Laser.