Investigation On 2.0?m Spectroscopic Properties Of Rare Earth Ions Doped Germanate-tellurite Glass

Under the background of rapid development of laser technology,fiber laser has become an important direction of laser development,and laser has achieved a leap from visible to mid-infrared bands.Especially the mid-infrared 2?m band laser has important applications in the fields of human eye safety radar,environmental monitoring,biomedical and military,and has been paid more and more attention.Tm³⁺?1.8?m?and Ho³⁺?2?m?are commonly used rare earth luminescent ions at 2?m.Up to now,rare earth doped 2?m band laser materials at home and abroad are mainly concentrated in crystals,quartz glass,silicate glass and fluoride glass materials.Tellurium germanate glass combines the advantages of tellurite and germanate glass: good chemical stability,high refractive index,wide infrared transmission range,low phonon energy,etc.It is suitable for a good laser material.Tellurium germanate glass also has the advantages of high adjustability of composition and high rare earth concentration.The main purpose of this paper is to study rare earth ion doped tellurium germanate glass matrix materials suitable for 2?m luminescence,and provide an excellent laser material for the future application of 2?m band single frequency laser and ultrashort pulse.This paper is divided into six chapters: the first chapter is the introduction;the second chapter is the experimental content and theoretical calculation;the third chapter is the study of Te-Ge glass matrix;the fourth chapter is the spectral characteristics of rare earth ion-doped Ge-Te glass at 2?m;the fifth chapter is the spectral characteristics of rare earth ion-doped Ge-Te glass at 2?m.The third,fourth and fifth chapters are the important parts of the paper,and the last chapter is the summary.The first chapter is the literature review.Firstly,the application,background and significance of 2?m optical fiber laser are introduced.Secondly,the luminescent ions and glass matrix materials in mid-infrared band are described.On this basis,the contents and ideas of this paper are proposed.The second chapter is about the experimental methods and theoretical basis.The preparation of germanium tellurite glass samples,experimental methods,physical and chemical properties testing,and spectral theoretical calculation and analysis methods are introducedChapter 3 is the study of glass matrix of two systems,germanium tellurite glass matrix and germanium tellurite glass matrix.The formulations of two systems of germanium tellurite glass were prepared by melting at high temperature.The physical and thermal properties of the glasses in the two systems of tellurium germanate were tested.The better properties of 70 Ge O₂-10 Te O₂-10K₂CO₃-5Nb₂O₅-5La₂O₃?GTNL?and 70 Te O₂-10 Ge O₂-10KO₂-7Nb2O5-3Ti₂O₃?TGNT?were obtained.The Tg of the two systems were 538? and 379?and ?T was 188? and 158?,respectively.The fourth chapter is about the spectral characteristics of rare earth ion-doped germanium tellurite glass at 2?m,Tm³⁺/Yb³⁺ and Tm³⁺/Bi³⁺ co-doped germanium-tellurite glass samples were prepared and studied.The following conclusions are drawn:1.Study of Yb³⁺ ion enhanced luminescence of Tm³⁺ ion at 2?m band.According to the J-O theory and the measured absorption spectra,the strength parameter?t?t=2,4,6?of Tm³⁺ ions in germanium tellurite glasses can be calculated.Then,the spontaneous emission transition probability,fluorescence branch ratio and radiation lifetime of Tm³⁺ ions are calculated.The fluorescence spectra of GTNLT2 glass samples were measured under the excitation of 980 nm LD pump source.When the doping concentration of Tm³⁺ ions was 0.25 mol%,the fluorescence intensity was the strongest.The emission and absorption cross sections of Tm³⁺ ions were calculated based on fluorescence spectra and Fuchbauer-Ladenburg theory.The values were 1.35?10^-20cm² and 0.566?10^-20cm²,respectively.In addition,the fluorescence decay lifetime of Tm³⁺ ion ³F₄ level was measured and calculated to be 2.38 ms.The energy transfer process between Tm³⁺ and Yb³⁺ was analyzed by Forster and Dexter theory and formula?2-26?.The microcosmic coefficients of Yb³⁺: ²F_5/2 ?Tm³⁺: ³H₅ were calculated to be 1.3826×10^-40.2.Study of Bi³⁺ ion enhanced luminescence of Tm³⁺ ion at 2?m band.Absorption spectra of Tm³⁺ doped,Bi³⁺ doped and Tm³⁺/Bi³⁺ co-doped germanium-tellurite glasses were obtained by testing.The spontaneous emission transition probability and radiation lifetime were further analyzed.Under the excitation of 980 nm LD pump source,the fluorescence spectra of different Tm³⁺ ion doping concentration were obtained.From the fluorescence spectra,the optimum Tm³⁺ ion doping concentration was 0.3mol%,and the fluorescence half-width?FWHM?was as high as 248 nm.According to the energy level diagram of Tm³⁺ ion and Bi³⁺ ion,the energy transfer mechanism between Tm³⁺ ion and Bi³⁺ ion is analyzed.On the basis of F-L formula,the maximum emission cross section of Tm³⁺ ion is obtained to be 2.89?10^-20cm².Finally,the fluorescence lifetime of ³F₄ level is 1.62 ms when the doping concentration of Tm³⁺ ions is 0.3mol%.Chapter 5: Spectral properties of rare earth ion doped Tellurium Germanate Glass at 2um,Ho³⁺/Yb³⁺ Co-doped Tellurium Germanate Glass samples were prepared and studied.The following conclusions are drawn:3.Yb³⁺ ions enhance the luminescence properties of Ho³⁺ ions at 2?m band.On the basis of absorption spectra and J-O theory,the intensity parameters?t?t=2,4,6?and spontaneous radiation transition probability?98.793s-1?and radiation lifetime?7.34ms?of Ho³⁺ ions were calculated.Under the excitation of 980 nm LD pumping source,the optimum doping concentration of Ho³⁺ ion was 1 mol at the strongest fluorescence intensity.The fluorescence quenched with the increase of doping concentration of Ho³⁺ ion.According to Fuchbauer-Ladenburg theory and fluorescence spectra,the emission cross section(0.32?10^-20cm²)of Ho³⁺ ion was calculated,and the maximum gain coefficient?0.15cm-1?was further calculated.When P>0.3,the gain coefficient began to change to positive value.Finally,the fluorescence lifetime of Ho³⁺ :⁵I₇ level is 2.78 ms.Chapter 6 is the conclusion of the paper,which summarizes the experimental results of the whole paper,and points out the shortcomings of the research work and the prospects for future work.