Quantification Of Absolute Spectral Parameter Of Up-conversion Fluorescence In Holmium Ions And Erbium Ions Doped Aluminum Germanate Glasses

In the past decades,glasses doped with one or more RE ions are becoming more and more useful in variety of linear and nonlinear optical applications,including color displays,commumications,laser su geries,phosphors,medical diagostics,etc.Among various rare-earth ions,trivalent holmium Ho3+ and erbium Er3+ have unique energy level structure,and unique characteristic emission in the visible region and near infrared region.Rare earth ions Ho3+ and Er3+ have much abundant energy,light in the visible features,and can be easily by other rare earth ion sensitive into to get strong glow in the visible area.Rare earth Ho3+/Yb3+doped on conversion luminescence material due to its in the visible region has color bright red light and green light emission and attention;.Rare earth Er3+ is also ole of the most important 1 frequency reactive ion,have abundant energy level structure,the spectral line focused on the 4S3/2,2H11/2 and 4F9/2 to the ground state energy level transition,Yb3+ ions at the same time as a sensitizer can improve the pumping efficiency of mixed Er3+ glass.Effects of rare earth ions of luminous efficiency is an important factor in material matrix phonon energy,the smaller the maximum phonon energy of the matrix,the radiation relaxation rate,the smaller,the higher the luminous efficiency.Oxide glass because of its higher solubility and stability of the chemical properties of received extensive attention of the researchers,among the oxide glass,germanate glass with relatively low phonon energy(about 820 cm-1),with good mechanical work ability and unique optical characteristics,is a good substrate material manufacturing integrated optoelectronic devices.In the traditional relative spectral measurement of the past,though to some extent,reflects the fluorescence properties of materials,but there are still some shortcomings,such as not accurate material quantitative fluorescence photons,however rare earth doped germanate glass fluorescent photons absolute characterization,more beneficial to evaluate the potential of its application in high quality light emitting devices,have very strong theoret'ical and practical significance of reference,such as efficient medical light source,and at the same time can provide data for waveguide light source device research and development to improve reference.Ho3+/Yb3+and Er3+/Yb3+doped is suitable for the preparation of optical waveguide.The results of this work is listed in the following:The tellurite glasses are chose to the basic glass host.As in the oxide glasses,the maximum phonon energy of the tellurite glasses is lower than those in other oxide glasses.Hence,RE ions can acquire efficient luminescence in tellurite glasses due to the lower phonon energy.The tellurite glasses exhibit good mechanical strength and high thermal stability for the non-oxide glasses,the glasses are expected to possess easier process for glass melting and optical fiber drawing.The followings are results this work achieved:1.Ho3+-doped and Ho3+/Yb3+-doped NMAG glasses have been designed and fabricated using high temperature fusion method.The radiative transitions can be analyzed by the Judd-Ofelt(J-O)theory based on the absorption of Ho3+,J-O parameters are derived to be ?2=7.47 x 10-20cm2,?4=2.58 x 10-20cm2and ?6=1.07 x 10-20cm2,respectively.Using these intensity parameters,some important radiation properties including spontaneous transition probabilities,branching ratios,and radiative lifetimes for the optical transitions of Ho3+ in NMAG glasses are calculated.Ho3+/Yb3+ doped germanate glasses adapting for K+-Na+ ion-exchanged waveguide were fabricated.Upconversion fluorescence has been measured by absolute spectral measurement system under 975 nm diode laser excitation.Net absorption and emission photon distributions and quantum yields were derived from absolute spectral power distributions.Experimental and calculation results revealed that the effective diffusion coefficient of K+-Na+ thermal ion-exchange is 0.068 ?m2/min,when Ho3+/Yb3+ doped germanate glasses are immersed in KNO3 molten salt at 370? for 4 hours,Ho3+ in germanate glasses emits 548nm green and 660nm red fluorescence,and the red one plays dominant role.The absolute spectral powers and the net emission photon numbers of the red upconversion emission are 28.03 ?W and 9.26×1013 cps,when pump power density is adjusted to 1227 W/cm2.The fluorescence quantum yields of 548 nm green and 660 nm red emissions are 0.17 x 10-5 and 2.41 x 10-5,respectively,and the total quantum yield in the visible region can reach to be 2.61 x 10-5 simultaneously.The slope of logarithmic curve of net emission photon number versus excitation power density indicate that the red and green upconversion emissions in Ho3+/Yb33+ doped germanate glasses are both due to two-photon excitation processes.Absolute characterization for the upconversion fluorescence from Ho3+ in waveguide-typed germanate glasses have been achieved,which provides reliable reference in developing rare earth optoelectronic functional materials.2.Er3+/Yb3+-doped NMAG glasses have been designed and fabricated using high temperature fusion method.The radiative transitions belonging to the 4f2 configuration can be analyzed by the Judd-Ofelt theory based on the absorption of Er3+.Judd-Ofelt intensity parameters are derived to be ? 2=7.17 × 10-20cm2,?4=1.97 × 10-20cm2 and 2 6=8.49 × 10-21cm2 by a least-squares fitting approach,respectively,and the J-O intensity parameters are important to investigate the local structure and bonding in the vicinity of rare earth ions.Using these intensity parameters,some important radiation properties including spontaneous transition probabilities,branching ratios,and radiative lifetime for the optical transitions of Er3+in NMAG glasses are calculated.Absolute spectral power distribution and net emission photon distribution of Er3+/Yb3+ doped waveguide-type aluminum germinate glasses were investigated,and the absolute quantification of upconversion fluorescence parameters had been realized.Power distribution of upconversion fluorescence was determined by absolute spectral measurement system with 975 nm excitation,from which the net absorption/emission photon distributions and the quantum yields were derived.Results show that the effective diffusion rate of K+-Na+thermal ion-exchange in glass sample is 0.077 ? m2/min.Two-photon excitation process can be assigned to the intense green and red emissions centered at 548 and 661 nm.The outputting power and the net emission photon of dominant red emission are 47.86 ?W and 16.03×1013 cps,respectively,when pumping power is selected as 1227 W/cm2.Compared with the relative measurement method whose quantum yield(QY)magnitude in germanate glass stays within the scope of 10-6?10-5,absolute method for photon quantification further presents quantum yield accurately,which significantly improves the accuracy and repeatability of test parameters for upconversion fluorescence in waveguide-type aluminum germanate glasses.