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Investigation on the Correlation among Composition, Structure and Property of Yb~(3+) Doped Laser Glasses

Author: LiuShuJiang
Tutor: LuAnXian
School: Central South University
Course: Materials Science
Keywords: Yb3+ion laser glass thermo-mechanical property spectroscopic property structural model
CLC: TQ171.735
Type: PhD thesis
Year: 2006
Downloads: 269
Quote: 0
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Abstract


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 7mol%. The nonlinear refractive index n2 decreases but the gaincoefficient increases with increasing Al2O3 content from 7mol%to13mol%.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-sectionσemi and gain coefficientσemi·σm 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-sectionσemi, 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 mol%) glass, B3+ prefers to form [BO4] whichstrengthen network structure, whereas Zn2+ depolymerizes networkstructure as modifier when x≤20mol%. When B2O3 content is larger than20mol%, 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-sectionσemi has maximum value of 0.816 pm2 atx=15mol%, therefore the glass has maximal gain coefficientσemi·τm.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-sectionσemi and gain coefficientσemi·τm.Compared with QX/Yb and FP laser glasses, the comprehensiveproperties of the fluorophosphate glassⅢ-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.

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