Investigation on Upconversion Luminescence of Tm^(3+)/Yb^(3+)-Codoped Oxychloride Tellurite Glasses

Tm^3 ＋/Yb^3 ＋-codoped oxychloride tellurite glasses were prepared. Thermal stability, Raman spectra and upconversion luminescence spectra were studied, and upconversion luminescence mechanisms were analyzed. The results show that the intense blue and relatively weak red emissions centered at 476 and 649 nm corresponding to the transitions ^1G4→^3H6 and ^1G4→^3H4 of Tm^3＋ , respectively, were simultaneously observed at room temperature under 980 nm LD excitation. With increasing while PbCl2 content, thermal stability of host glasses increases, phonon energy of host glasses decreases, and upconversion luminescence intensities increase, which indicate that Tm^3＋/ Yb^3＋-codoped oxychloride tellurite glasses can be used as potential host materials for upconversion blue lasers.

Influence of Coordinate Field Index on Upconversion Luminescence in Er ^(3+) Doped Tellurite Glasses

The upconversion luminescence in Er 3+ doped tellurite glasses (MKT: TeO_2-MgO-K_2O) were performed. Two green emission bands at 521 and 550 nm, corresponding to the 2H_ 11/2→4I_ 15/2 and 4S_ 3/2→4I_ 15/2 transitions, respectively, were observed. Coordinate field index, which was proposed by deducing from Pauling′s rules on the basis of Zachariasen′s random network theory, can be used to rationalize the remarkable variation in the intensity of upconversion luminescence.

Spectroscopic Properties of Nd^(3+)-Doped Tellurite Glasses

The Nd^3＋-doped pared. The absorption and tellurite glasses were preemission spectra of Nd^3 ＋- doped tellurite glasses at room temperature were measured. The Judd-Ofelt parameters （Ω2, Ω4, Ω6） of the glasses were calculated from measured absorption spectra. The calculation results of luminescence properties （A, β, τrad, σ） of Nd^3＋ ions in the tellurite were glasses were given. Spectroscopic properties, concentration quenching in these kinds of the glasses were investigated. The results indicate that the tellurite glasses with composition of 70% TeO2, 20% ZnO, （ 10 - x ） % La2O3, x % Nd2O3 （ mol% ） show high emission cross section and low phonon energy. The fluorescent intensity and the emission cross section have a maxi- mum value at x = 0.5, namely, the optimum Nd^3 ＋ ion concentration in the tellurite glass is 0.5% （1.93 × 10^20 ions·cm^-3）. The fluorescence properties of Nd^3＋ measured are basically in accord with the calculated results.

Thermal Stability and Raman Scattering Spectra of Tellurite Glasses for Broadband Fiber Raman Amplifiers

The glass transition temperature （T）, crystallization onset temperature （T） and Raman scattering spectra of new tellurite glasses were studied as the function of glass composition. With the introduction of other metal oxides such as Nb2O5, BaO and WO3, T temperature increases, the intensity of exothermal peaks decreases, and thermal stability of tellurite glass improves. It was found that more TeO3 units transformed into TeO4 units and non-bridging oxygen atoms decreased with the incorporating other metal oxides in glassy network, when the content of TeO2 was fixed. Appearance of peak at 920 cm^-1 broadens the Raman bandwidth of tellurite glasses, which is very useful realize high efficient broadband fiber Raman amplifiers.

Three-color upconversion luminescence of rare earth codoped oxyhalide tellurite glasses

The red, green, and blue upconversion properties of Er^3＋/Tm^3＋/Yb^3＋-codoped oxyhalide tellurite glasses were studied under 980 nm LD excitation. The intense red （657 nm）, green （530 and 545 nm）, and blue （476 nm） emissions were simultaneously observed at room temperature. The results showed that the mixed halide modified tellurite glass （TZFCB） had strong upconversion emissions. The effect of halide on upconversion intensity was observed and discussed, and possible upconversion mechanisms were evaluated. The intense red, green, and blue upconversion luminescence of Er^3＋/Tm^3＋/Yb^3＋-codoped oxyhalide tellurite glasses might be a potentially useful material for developing three-dimensional displays applications.

Spectroscopic properties of Yb^(3+)-doped TeO_2–BaO–BaF_2–Nb_2O_5-based oxyfluoride tellurite glasses

A series of oxyfluoride glasses with the compositions of 75 mol% TeO2, 10 mol% Nb2O5, （15 mol%-x） BaO, x BaF2 （x =0 mol%, 5 mol%, 10 mol%, 15 mol%） doped with Yb2O3 were prepared by the melt-quenching method. Their emission cross-sections, fluorescence lifetimes, and gain properties were investigated by using the absorption spectra and the fluorescence decay curves. The results show that by substituting BaF2 for BaO, the emission cross-section decreases from 1.37 pm^2 to 1.21 pm^2, and the fluorescence lifetime increases from 0.71 ms to 0.96 ms. These properties indicate that this oxyfluoride tellurite glass may have potential uses as the Yb2O3-doped gain medium in a solid laser.

The effect of OH^(-) groups on the spectroscopic properties of erbium-doped tellurite glasses

A series of five different concentration erbium-doped tellurite glasses with various hydroxl groups were prepared. Infrared spectra of glasses were measured. In order to estimate the exact content of OH? groups in samples, various absorption coefficients of the OH? vibration band were analyzed under the different oxygen bubbling times. The absorption spectra of the glasses were measured, and the Judd-Ofelt intensity parameters ?i of samples with the different erbium ions concentration and OH? contents were calculated on the basis of the Judd-Ofelt theory. The peak stimulated emission cross-section of 4I13/2→4I15/2 transition of the samples was finally calculated by using the McCumber theory. The fluorescence spectra of Er3+:4I13/2→4I15/2 transition and the lifetime of Er3+:4I13/2 level of the samples were measured. The effects of OH? groups on the spectroscopic properties of Er3+ doped samples with the different concentrations were discussed. The results showed that the OH? groups had great influences on the Er3+ lifetime and the fluorescence peak intensity. The OH? group is a main influence factor of fluorescence quenching when the doping concentration of Er2O3 is smaller than 1.0 mol%, but higher after this concentration, the energy transfer of Er3+ ions turns into the main function of the fluorescence quenching. And basically, there is no influence on the other spectroscopic properties (FWHM, absorption spectra, peak stimulated emission cross section, etc.).

Synthesis of praseodymium trioxide doped lead-boro-tellurite glasses and their optical and physical properties

This paper presents the influence of TeO_(2) on the optical and physical properties of rare earth ion Pr^(3+) doped 75PbO-(24-x)B_(2)O_(3-x)TeO_(2)-1Pr_(2)O_(3) glass matrix.Using the absorption coefficient measurements,optical band gap energies of the studied glasses are estimated.Oxide ion polarizability,refractive index,optical basicity,reflection loss and transmission coefficient are discussed and reported for the investigated glasses.Physical parameters like the optical dielectric constant,polaron radius,interatomic separation,molar refraction and the metallization criterion are also studied through molar density and molar volume.The FTIR analysis reveals the shift of the band appearing at 1029 to 870 cm^(-1) because of the high concentration of PbO(75 mol% in the present glass)in the matrix.The Pb-O-B linkage is considered to be the important in the network structure of these glasses.For the present glasses metallization parameter values are<1.The polarizability values are high but decrease with increasing value of TeO_(2) concentration.This may be due to densification of restricted or localized states caused by the creation of dangling bonds.

Design and achieving of multicolor upconversion emission based on rare-earth doped tellurite glasses

yD3＋/Tm3＋ co-doped and yD3＋/Ho3＋/Tm3＋ tri-doped tellurite glasses were synthesized by fusing the mixture of TeO2, PbF2, AIF3, BaF2, Yb2O3, Tm203 and H0203 in a cortmdum crucible at 850 ℃ for 20 min. The synthesized glasses were characterized by upconversion emission spectra under the excitation of 980 nm laser, and the emission colors were investigated according to the CIE-1931 standards. The results indicated that yD3＋/Tm3＋ co-doped tellurite glass exhibited blue upconversion emission with favor- able color coordinates of （0.20, 0.07）. Yb3＋, HO3＋ and Tm3＋ tri-doped tellurite glasses presented white upconversion luminescence under a single 980 nm laser excitation. Moreover, a very wide range of emission colors could be tuned by altering Ho3＋ concentration. Combining the contribution of adjusting Ho3＋ concentration and pump power, near equal energy white light was obtained.

Spectroscopic investigations on Yb^3+ doped and Pr^3+/Yb^3+ codoped tellurite glasses for photonic applications

In this work we repo rt on structural and spect roscopic properties of Yb^3+doped and Pr^3+/Yb^3+co-doped TeO2-Bi2 O3-ZnO-Li2 O-Nb2 O5(TBZLN)tellurite glasses.Bending and stretching modes of TeO2 and Te-OH bond(strong and weak)were analysed from the deconvolution of observed Raman and FT-IR spectra.Based on the absorption measurements,the energy bands of Yb^3+and Pr^3+ions are assigned.The spectroscopic properties for the radiative transitions of Yb^3+and Pr^3+ions were reported using McCumber and Judd-Ofelt theories.Visible emission bands originating from 3 P1 and 3 P0 to lower lying levels of Pr^3+were registered under 447 nm excitation.The emission band around 1334 nm assigned to the Pr3:1 G4→3 H5 was observed when excited at 980 nm.The stimulated emission cross-section(σemi(λ))and effective linewidth(Δλeff)for the 3 P1→3 H6,3 P1→3 H5,3 P0→3 H6,3 P0→3 F2,3 P1→3 F3,3 P1→3 F4,3 P0→3 F4 and 1 G4→3 H5 transitions of Pr^3+are reported.Upconversion luminescence in Pr^3+/Yb^3+codoped glass upon 980 nm excitation was measured.Possible resonant transfer processes between Yb^3+and Pr^3+ions are presented and discussed.The chromaticity co-ordinates were also evaluated from the visible emission spectra showing that Pr^3+/Yb^3+co-doped glass may be suitable for the development of yellow-orange(λexc=447 nm)and near white light(λexc=980 nm)emitting devices in photonics.

Preparation of AgCl Nano-Crystal Embedded Tellurite Nonlinear Optical Glasses under Electric Field Accompanied Heat Treatment

The quantum effect of nano-crystals is an important factor to improve nonlinear optical performance of nanocrystal embedded glasses, while controlling the size distribution and content of nano-crystals in the glass accurately is a key to obtain good quality. The auxiliary direct current electric field, accompanied with heat treatment, was applied on AgCI containing niobic tellurite glass sheet. The nucleation and crystallization of the glass were well controlled under auxiliary electric field. It was found that the average size of AgCI nano-crystal particles in the glass is smaller than that under single heat treatment, and the content of nano- crystals is higher. Therefore the third-order nonlinear optical performance of the glass was increased a lot. The local-area distributed AgCl nano-crystal particles can also be embedded into a glass sheet by using locally applied electric field.

Improved Fluorescence from Tm^3＋/Er^3＋/Ce^3＋ Triply Doped Bismuth-Silicate Glasses for S＋C-bands Amplifiers

Fluorescence of Tm^3＋/Er^3＋ codoped bismuth-silica （BS） glasses and the sensitization of Ce^3＋ are investigated, It shows that Ce^3＋ codoping with Tm^3＋/Er^3＋ in BS glasses results in a quenching of Tm^3＋ ion emission from ^3F4 to the ^3H6 level. Consequently, the 1.47μm emission occurs after the population inversion between the ^3H4 and ^3F4 levels. Furthermore, the codoped glasses show the broad emission spectra over the whole S and C bands with full-width at half-maximum （FWHM） up to about 119nm, as it combines 1.55μm emission band of Er^3＋ with 1.47μm emission band of Tm^3＋ under 800hm excitation.

Effects of Yb^3＋ in Er^3＋/Yb^3＋ Codoped Fluorophosphate Glasses

For the Er^3＋ /Yb^3＋ codoped fluorophosphate glasses, Judd-Ofelt theory is used to analyse the influence of YbF3 as not a sensitizer but an average component on the spectroscopic properties around 1530nm emission. The double roles of Yb^3＋, as a sensitizer and as an average component, are discussed. It is found that Yb^3＋ as an average component contributes to the increase of fluorescence lifetime, and Yb^3＋ as a sensitizer has the best sensitization when its concentration is 2.4 mol%.

Thermal Analysis of Glasses in TeO2-BaF2-LaF3 Systems

Divalent metal fluorides MF2 （M=Sr, Mg, Ca） in oxyfluoride tellurite glasses TeO2-BaF2-LaF3 were synthesized. The densities, refractive indices and characteristic temperatures of synthesized glasses were measured. The influence of divalent metal fluorides-MF2（M=Sr, Mg, Ca） on the thermal stability of oxyfluoride tellurite glasses TeO2-BaF2-LaF3 were studied. Results show that the replacement of BaF2 by SrF2 and MgF2 can enhance the thermal stability against crystallization of the glass. A glass system with good thermal stability was produced, which could be a potential candidate for the host materials of the fiber devices.

Investigation on energy transfer from Er^(3+) to Nd^(3+) in tellurite glass

A study of energy transfer of Er^3＋/Nd^3＋ codoped tellurite glasses was presented. By Nd^3＋ co-doping, both the Er^3＋ green emission corresponding to the Er^3＋： （^4S3/2, ^2H11/2）→^4I15/2 transitions and the red emission corresponding to the Er^3＋： ^4F9/2→^4I15/2 transitions were quenched. The energy transfer mechanism between Er^3＋ and Nd^3＋ was discussed based on their energy level characteristics. The interaction parameters, CO-A, for the energy transfer processes from Er^3＋ to Nd^3＋ in tellurites glass were calculated. Finally, the resonant transfer Er^3＋： ^4I9/2→Nd^3＋： （^4F5/2, ^2H9/2） was proposed to be the most probable microscopic process to occur in contrast with the other processes.

Tm^(3+)-doped tellurite glass with Yb^(3+) energy sensitized for broadband amplifier at 1400–1700 nm bands

A kind of novel experiment was disclosed as it possessed two bands of fluorescence emission at 1.4 and 1.6 μm, which were perfectly complimentary to the current C band of optic communication. The fluorescence was based on energy transfer and up-conversion processes between Tm^3＋ and Yb^3＋ under direct pumping of 975 nm LD. The spectra and lifetimes of Tm^3＋ fluorescence in the tellurite glass were described. The corresponding fluorescence characteristics and energy migration process were analyzed by the method of lifetime and intensity comparison. The mechanism of the up-conversion based IR fluorescence was presented upon analyzing the multi-photon pumping process. The potential advantages of Tm^3＋/Yb^3＋ co-doped tellurite glass as amplifier material were concluded.

1.3 μm Emission from Nd^(3+)-doped Tellurite Glass Fiber

1 wt pct Nd2O3-doped tellurite bulk glass and fiber with the same composition of 75TeO2-15ZnO-5Na2O-5Li2O4(mol fraction, %) were fabricated. Judd-Ofelt analysis was carried out for the bulk. The emission from the 4F3/2→4I13/2 transition in fiber is at 1.33 μm wavelength with a spectral bandwidth of 55 nm, which is similar to that in bulk. In the case of the fiber, the lifetime of 4F3/2 Ievel is 164 μs, and the quantum efficiency is -100%. The figure-of-merit for gain (<δpTo) for Nd3+-doped tellurite glass is about 2.8×10-24 cm2·S, which is quite comparable vvith that in Nd3+-doped fluoroaluminate glasses, and is an order of magnitude larger than Pr3+-doped fluoride glasses.

Preparation and ASE Spectrum of a Single-Mode Erbium Doped Tellurite Glass Fiber with D-type Cladding Geometry

Based on the host of tellurite glasses, the glass formation, preform manufacture, and fiber fabrication are described. The characterization of amplified spontaneous emission (ASE) from this newly fabricated single-mode Er3+-doped tellurite fibers is also presented. When pumped at 980 nm, a very broad erbium ASE around 1.53 μm was observed. The variations of ASE with fiber length and pumping power are measured and discussed. The output of 2 mW from Er3+-doped tellurite fiber ASE source was obtained under the pump power of 660 mW.

Upconversion properties of Er^3＋/Yb^3＋ co-doped TeO2-Nb2O5-Li2O glasses

The Er^3＋/Yb^3＋ co-doped TeO2-Nb2O5-Li2O glass is prepared by conventional melting method, and its upconversion spectra are measured. The intense green upconversion luminescence upon excitation with a 976 nm laser diode is observed with the naked eyes. The dependence of luminescence intensity on the ratio of Yb^3＋/Er^3＋ is discussed in detail, and the relationship between the ratio of green luminescence intensity to red luminescence intensity and the ratio of Yb^3＋/Er^3＋ is also studied, The luminescence intensity increases with the ratio of Yb^3＋/Er^3＋ increasing. The ratio of Yb^3＋/Er^3＋ plays a more important role than the concentration of Er^3＋ in determining the upconversion luminescence intensity. The ratio of green luminescence intensity to red luminescence intensity reaches a maximum when ratio of Yb^3＋/Er^3＋ is 3. Thus the glass could be one of the potential candidates for LD pumping solid-state lasers.

Spectroscopic Properties of Er~ (3+), Yb^(3+)-Codoped Tellurite Glass-Ceramics Containing Nanocrystals

A transparent tellufite glass-ceramic containing nanocrystals based on the composition of 15Li2O-15Nb2O5-7OTeO2-0. 1ErEr2O3-0. 4Yb2O3 （mol%）was prepared by using a two-step heat-treatment. The XRD patterns show that the composition of crystals in glass-ceramics is possibly Yb6Te5O19.2 or Er6Te5O19.2, and the dimension of crystals is about 55 nm. The Judd-Ofeh parameters, Ωt, （t = 2, 4, 6）, and the spontaneous emission probability of Er^3＋ in glass and glass-ceramics were calculated from optical absorption spectra. The absorption cross section of Er^3 ：^4I15/2→I13/2 and the emission cross section of Er^3 ＋ ：^4I15/2→I13/2 in two samples were also calculated. Raman scattering spectra of glass and glass-ceramic were measured, the fluorescence spectra and the upconversion spectra of Er^3 ＋ ion in glass and glass-ceramic were compared.