Preparation And Properties Of Neodymium Ytterbium Doped Boron Germanate Glass

1064 nm laser has been widely used in high-tech fields such as laser guidance,image processing,and medical devices due to its strong tissue penetrating ability,low interference,high power,and high accuracy.The 980 nm band laser can become an important technical foundation for the application of blue/green light sources through frequency doubling output.Therefore,the development of multi band laser gain materials is of crucial significance.In this thesis,neodymium ytterbium doped borogermanate glass system is selected as the research object.By modulating the composition and ratio of the substrate,the luminescent intensity of borogermanate in the near infrared region is improved;Through the improved gradient cooling method,the preparation of low-temperature borogermanate optical glass was achieved,which reduced the sample production cost while reducing the volatilization loss of rare earths.According to J-O theoretical analysis,this material has the potential to achieve high laser gain coefficient and multi band output in the near infrared region.The specific research content is as follows:（1）In order to improve the luminous efficiency of rare earth doped borogermanate glass materials in the near infrared region and reduce the non radiative loss caused by the high phonon energy of borate(～1400 cm^-1),Ge O₂ was selected as the second substrate in this project to study the optical band gap and refractive index variation of the glass material,enabling the material to have the development potential to further improve near infrared luminescence.Finally,the ratio of the binary substrate was determined to be B₂O₃:Ge O₂=6:4.（2）A series of Nd³⁺doped ternary optical glasses with different alkali metal oxides were prepared at a temperature of 1300℃.The improvement mechanism of the glass ligand structure was analyzed through Fourier transform infrared spectroscopy and fluorescence spectroscopy studies while maintaining the constant ratio of B₂O₃ to Ge O₂.When the Ca O concentration reached 25 mol%,the glass network exhibited the coexistence of[Ge O₄],[Ge O₆],[BO₄],and[BO₃]coordination polyhedrons,The most suitable ligand structure for luminescence was obtained from this formulation.According to the calculation of optical basicity,Mg O doping has a great oxygen ion polarizability and exhibits a strong ionic bonding effect.In order to avoid the impact of optical alkalinity on subsequent luminescence intensity（the impact of optical alkalinity is greater than other effects）,Ca O was selected as the substrate for subsequent research.It was found that when the Ca O molar ratio was kept at 25 mol%,Nd₂O₃ reached the highest luminescence intensity at 1 mol%.（3）A series of Nd³⁺doped quaternary glasses with different trivalent metal oxides were prepared at a temperature of 1300℃.The optical performance parameters were quantified using J-O theory.Ω₂ was enhanced all the way to the sample of BGCAl5 and then decreased,showing coexistence of covalence and ionic properties.Ω₄ increases with the increase in the content of structural[Al O₄]and[Al O₆]units.With the increase ofΩ₆,the effect of the crystal field on Nd³⁺decreases,resulting in the broadening of the spectral lines of the fluorescence emission spectrum.The optical properties and laser quality parameters of Nd³⁺ions in BGCAl1-6 glass were characterized using J-O intensity parameters.BGCAl5 glass exhibited significant electrical dipole transition spectral line strengths S_ed of 7.02,18.53,and 10.04 for⁴F_3/2→⁴I_13/2,⁴F_3/2→⁴I_11/2,and ⁴F_3/2→⁴I_9/2,respectively×10^-21cm²,corresponding spontaneous emission probabilities are 203.90,1065.19,and 938.26s^-1,respectively,with a radiation lifetime of 0.454 ms,wherein ⁴F_3/2→⁴I_11/2 has the highest fluorescence branching ratio of48.03%.Effective fluorescence bandwidthΔλ_eff is 57.49 nm,with a stimulated emission cross sectionσ_em is 8.83×10^-20cm²,quality factorσ_em×τ_exp is 2.71×10^-23cm²s,gain bandwidthσ_em×Δλ_eff is 50.76×10^-26cm³,optical gainσ_em×τ_R=4.00×10^-23cm²s,saturation strength I_S is0.691×10⁸W/m²,indicating that BGCAl5 glass is at 1.053μm-band has good development potential.（4）A series of Yb³⁺doped tetravalent oxide pentavalent optical glasses were prepared at1200℃.After the introduction of Te O₂,the melting temperature of the glass material decreases,and Te O₂ as a network forming body makes the glass network more compact.When Te O₂ is 10 mol%and Yb³⁺is 0.6 mol%,the luminous intensity reaches the highest.When Te O₂ is 10 mol%,the glass network structure forms the coexistence of coordination polyhedrons such as[BO₄],[BO₃],[Ge O₄],and[Ge O₆],and the content of[Te O₄]triangular bipyramidal groups is higher,the glass system structure is more compact,and the network asymmetry is more conducive to fluorescence radiation.（5）A series of Yb³⁺/Nd³⁺double doped glass materials were prepared at 1200℃.The material exhibits strong absorption peaks at both 808 nm and 980 nm(Yb:²F_7/2→²F_5/2)wavelengths,indicating that Nd³⁺and Yb³⁺are evenly and ideally distributed in the glass network,and there is no local ligand field clustering phenomenon.Through fluorescence spectroscopy research,under excitation at 808 nm,with the increase of Yb³⁺concentration,the luminous intensity at 1060 nm continues to decrease,while at 981 nm,the luminous intensity shows a trend of first increasing and then decreasing.The highest luminous intensity corresponds to 2 mol%,indicating that there is energy transfer between Nd³⁺and Yb³⁺,and the energy transfer mechanism is the realization of multi band emission through dipole dipole interaction.With the negative charge of[Al O₄]unit in Nd³⁺/Yb³⁺co-doped glass samples,Al³⁺-O-Nd³⁺bonds are easy to form,thereby promoting Nd³⁺/Yb³⁺energy transfer to form interactive energy clusters,which is conducive to high concentration doping of Yb³⁺,and the concentration of Yb³⁺doping is 3.33 times that of single doping.