Investigation On 2μm Spectroscopic Properties Of Rare Earth Ions Doped Silicate Glasses

Laser has achieved rapid development from the visible to infrared area.In particular,2μm laser has played an irreplaceable role in the military,space communications,medical and environmental monitoring.At present,the researches of rare earth doped laser materials mainly concentrated in the crystal,silica glass,silicate glass,heavy metal oxide and fluoride glasses.Compared with other matrices,silicate glass emerged as good mid-infrared fiber laser materials beacuse it combined the low expansion coefficient,excellent mechanical strength and good thermal stability.In this paper,several kinds of rare earth ions doped silicate glass samples were prepared by adjusting the compositions and the preparation technology.This process provided the theoretical and experimental basis for subsequent optical fiber drawing and laser output.This dissertation included the following five chapters.The first chapter was literature review,the principles and the compositions of glass,the light-emitting mechanisms of rare earth ions and main applications of 2μm laser were introduced.The silicate glass and other glass matrices structure characteristics and the latest research results were presented in detail,and finally we put forward the main research ideas and methods in this paper.The second chapter was experiment methods and theory calculations,including the preparation procedures of silicate glasses,measurements of the physical,spectroscopic properties and theory analyses.The third chapter mainly studied the physical and chemical properties of silicate glass.A series of silicate glasses with different components were prepared,the density,refractive index and differential thermal stability were analyzed.According to theΔT,SBL,SCK,SAC and SPB components were selected as main systems.After reheat treatment under 900℃,SCK and SPB were devitrification crystal,the SBL and SAC samples were transparency,thus they owned good resistance to crystallization.There were no obvious crystallization peaks observed in SAC and SBL components by X-ray diffraction experiment.The fourth chapter was the main content of this thesis.Different concentrations of Tm₂O₃ were doped into the SAC and SBL glass matrixes,the J-O parameters and the spectrum parameters such as fluorescence branching ratio,transition probability of the spontaneous radiation were calculated by the theory of Judd-Ofelt.The fluorescence spectra of Tm³⁺doped silicate glasses were measured.The maximal fluorescence intensity was occurred when the doping concentration of Tm³⁺reaches 2mol%.The stimulated emission cross section of Tm³⁺:³F₄→³H₆ was calculated to be 9.7×10^-21cm².Based on the Tm³⁺singly doped,Tm³⁺/Yb³⁺,Er³⁺/Tm³⁺,Tm³⁺/Ho³⁺and Ho³⁺/Yb³⁺double doped silicate glasses were analyzed in detail.The energy transfer processes of Tm³⁺/Yb³⁺codoped silicate were discussed,and the J-O parameters and the energy transfer coefficients were calculated.Pumped by the 808 and 980nm LD,the 1.8μm emission of Tm³⁺was observed in Er³⁺/Tm³⁺double doped silicate glass,the optimum doping ratio of Er³⁺/Tm³⁺was 3:2.The energy transfer mechanisms between the Er³⁺and Tm³⁺were discussed in detail.By testing the lifetime of Er³⁺,the Er³⁺:⁴I_13/2→Tm³⁺:³F₄ level energy transfer efficiency was as high as 91.2%.It was found that in Tm³⁺/Ho³⁺codoped silicate glass,with the introduction of fluoride,OH^-content was greatly reduced.When content of BaF₂ was 15mol%,the hydroxyl coefficientα^-_OH was 0.545cm^-1.The stimulated emission cross sections of Tm³⁺and Ho³⁺were 8.25×10^-21cm² and 7.33×10^-21cm²,respectively.Finally,the strong 2μm emission was achieved through the way of Ho³⁺/Yb³⁺codoping.The stimulated emission cross section of Ho³⁺:⁵I₇→⁵I₈ was 5.04×10^-21cm².The micro energy transfer coefficient of Yb³⁺:²F_5/2 level to Ho³⁺:⁵I₆ level was 2.3×10^-40cm⁶/s.The above results showed that the Tm³⁺/Yb³⁺,Er³⁺/Tm³⁺,Tm³⁺/Ho³⁺and Ho³⁺/Yb³⁺can effectively enhance the 2μm emission of rare earth ions.In conclusion part,the full text of the experimental results and the problems were summarized.