Effect Of Germanate Glasses Fluorescence Properties Of Rare Earth Ion-doped Optical Basicity

Rare-earth (RE) ions are proper activators in the photoluminescence materials due to their abundant energy levels and physical-chemical properties. The RE doped upconversion materials have potential applications in solid-state lasers, color display and information processing. Optical fiber telecommunication benefits a lot from the invention of EDFA. It should be noted that a key consideration of RE ions doped material applications is the photoluminescence efficiency since every application need high signal-noise ratio. However, at the current stage, efficiency of rare-earth doped material luminescence is still fairly low, which greatly restricts its applications.This thesis provides a comprehensive review on the upconversion, near-infrared lunminescence (NIR) and downconversion luminescence characteristics of RE ions doped materials, gives an overview of the recent progress and problems,and puts forwards their future research directions. The effect of optical basicity and struc on the upconversion, NIR, downcoversion lunminescence is inversitigated, to develop the novel light source with the typical characteristics of "estimate" and "tunable". Thermal analysis (DTA), IR absorption spectra, Raman spectra, Absorption spectra, photoluminescence spectropy (PL) were used to study the structure and lunminescence properties of the materials. A series of important conclusions and innovative results with practical significancewere obtained.The structure of alkali metal and alkali earth germanate glass are investigated. With the alkali metal and alkali earth ions increase, result in breaking the Ge-O-Ge bonds and forming Ge-O-, there are more and more NBOs in the structure, the O/Ge ratio increases and most of O2-get involoved in transition from [GeO4] to [GeO6]. And the refractive index of germanate glass under different excitation wavelengths are increased.The effect of optical basicity on the Er3+-doped germanate glasses is investigated. The materials optical basity changes by adjusting network modification of ionic radius and the concertion. It is found that, the red and green upconversion luminescence decreased with the optical basicity inceased, under980nm semiconductor laser excitation. In the alkali metal germanate glasses, the red upconversion luminescence intensity is higer than green, comparing with green up-conversion luminescence, the red up-conversion luminescence intensity decreases rapidly with increasing optical basicity, and The color of up-conversion luminescence changed from red to green. The green upconversion luminescence mechanisms is ESA, and the red is ESA, energy transfer and the non-radiative process from4S3/2level. With the optical basicity increased, the Ω6decreased, the population at the4I13/2level decreased, and then the upconversion lunminescence intensity decreased. On the other hand, the red lunminescence intensity decreased remarkably due to that, the optical basicity increased, these changes indicate that the covalency of the Er-O bond decreases, the energy transfer effecity decreased.Effect of optical basicity on broadband infrared fluorescence in Er3+-doped, Tm3+-doped, Bi-doped germanate glasses are investigated, respectively. The materials optical basity changes by adjusting network modification of ionic radius and the concertion. The study found that, the emission intensity at1.55μm in Er3+-doped germanate glass is decreased, with the increasing of optical basicity, and the Ω6, the absorption, emission cross-sections, the radiative lifetime of Er3+at the excited level4I13/2and FWHM are decreased, under980nm excitation. The effect of optical basicity on Tm3+-doped germanate glasses is same with Er3+-doped. Finally, under808nm excitation, with the optical basicity increasing, the1300nm lunminescence intensity of Bi-doped germanate glasses decreased and the FWHM increased, the NIR emission from900nm to2000nm. Under690nm excitation, it is appeared two peak position (1200nm and1400nm, respectively.) with the optical basicity increasing, the peak position move to long wavelength, the FWHM increased and higher to428nm. Through our research, the optical bacsicity could change the luminescence intensity and the FWHM.The dependence of optical basicity and Bi/Yb3+co-doped germanate glasses is also study. The optical basicity changes by adding the concertion of Yb+ion. The result shows that, under808nm excitation, there are two peaks, Bi ion of1300nm and Yb3+of1030nm which is due to the ET from Bi ion, respectively. The1300nm emission intensity of Bi ion decreased, because of the ET and optical basicity increasing. The Yb3+ion of1030nm firstly increased and then decreased with the optical basicity increase.under690nm excitation, there are three peaks, Bi ion of1300nm and1160nm, and Yb3+of1030nm which is due to the ET from Bi ion, respectively, the optical basicity increase and ET from Yb3+ion to Bi ion cause the higher1160nm NIR luminescence, the optical basicity increase and ET from Bi ion to Yb3+ion cause the lower1300nm NIR, but the effect of optical basicity on the NIR lunminescence is dominate, and lastly lead to the NIR lunminescence intensity decresed. Finally, the ET from Yb3+ion to1160nm of Bi ion is proved.