Doped Phosphate Glasses Research Articles

Optical absorption and photoluminescence studies of Eu 3+-doped phosphate and fluorophosphate glasses

Phosphate (P 2O 5+K 2O+BaO+Al 2O 3+Eu 2O 3) and fluorophosphate (P 2O 5+K 2O+BaO+BaF 2+Al 2O 3+Eu 2O 3) glasses with different Eu 3+ ion concentrations have been prepared and characterized through optical absorption, photoluminescence and decay times. An intense red luminescence is observed from the 5D 0 emitting level of Eu 3+ ions in these glasses. The relative luminescence intensity ratio of 5D 0→ 7F 2→ 5D 0→ 7F 1 transitions has been evaluated to estimate the local site symmetry around the Eu 3+ ions. The emission spectra of these glasses show a complete removal of degeneracy for the 5D 0→ 7F 1 and 5D 0→ 7F 2 transitions. Second and fourth rank crystal-field (CF) parameters have been calculated together with the CF strength parameter by assuming the C 2v symmetry for the Eu 3+ ions in both the phosphate and fluorophosphate glasses. Judd–Ofelt parameters have been evaluated from the luminescence intensity ratios of 5D 0→ 7F J ( J=2, 4 and 6) to 5D 0→ 7F 1 transitions. These parameters have been used to derive radiative properties such as transition probabilities, branching ratios, radiative lifetimes and peak stimulated emission cross-sections for the 5D 0→ 7F J transitions. Decay curves of the 5D 0 level of Eu 3+ ions in these two Eu 3+:glass systems have been measured by monitoring the 5D 0→ 7F 2 transition (611 nm) at room temperature. The experimental lifetime of the 5D 0 level in the title glasses is found to be higher than Eu 3+-doped niobium phosphate glasses. The analysis indicates that the lifetime of the 5D 0 level is found to be less sensitive to the Eu 3+ ion concentration and addition of BaF 2 has no significant effect on the optical properties of Eu 3+-doped phosphate glasses.

Ultraviolet–visible absorption of gamma-irradiated transition metal ions doped in sodium metaphosphate glasses

Spectrophotometric studies of sodium metaphosphate glasses doped with 3d transition metals (0.1% Ti → Cu) were carried out before and after successive gamma irradiation. In the undoped glass, strong charge-transfer ultraviolet absorption bands are observed and are related to trace iron impurities in the raw materials used for glass preparation. These charge-transfer bands are observed to interfere or mask the characteristic ultraviolet bands due to some of the transition metals which possess ultraviolet absorption. Gamma irradiation produces characteristic induced bands in the base undoped and TM doped phosphate glasses. The response of the glasses to gamma irradiation is related to the creation of numerous induced defect color centers, the approach of a saturation condition and the possible photochemical effect on the transition metal ions.

Dehydration of Er 3+-doped phosphate glasses using reactive agent bubble flow method

This paper investigated on the dehydration of Er 3+-doped phosphate glasses using O 2 + CCl 4 bubble flow method. The influence of parameters of dehydration effect was studied systemically. It was found that the dehydration rate was rather rapidly at the initial stage of bubbling. Increasing gas flow rate and temperature could drive the dehydration process toward lower OH concentration in the melts. The dehydration process was carried out in open system and analyzed by thermodynamic theory of open system, which clarified the process of eliminating of OH groups from the glass melts with bubbling time and gas flow rate. A time-dependent empirical equation about reaction rate constant was derived, and the relationships between rate constant and bubbling flow rate, and temperature were also discussed. This analytical method could be applicable to the dehydration of glass melt using other dehydration agents.

Gain Characteristics of Er3+-Doped Phosphate GlassFibres

An erbium-doped phosphate glass fibre has been drawn by the rod-in-tubetechnique in our laboratory. The gain for the Er3+-doped phosphateglass fibre with different pump powers and with different input signalwavelengths is investigated. The 2.2-cm-long fibre, pumped by asingle-mode 980-nm fibre-pigtailed laser diode, can provide a net gainper unit length greater than 1.8 dB/cm. The pump threshold is about50 mW at the wavelength of 1534 nm, and below 70 mW at 1550 nm. Thegain linewidth of the Er3+-doped phosphate glass fibre is greaterthan 34 nm and can cover the C band in optical communication networks.

Difference of Properties between Yb<sup>3+</sup>-Doped Silicate and Phosphate Laser Glasses

The Yb3+-doped silicate and phosphate laser glasses were prepared by using of traditional melt quenching technology, and the physical and spectral properties were investigated. The results show that the stimulated emission cross section and the fluorescence lifetime are 0.67×10-20cm2 and 1200μs for the silicate glass, and 0.75×10-20cm2 and 1000μs for the phosphate glass respectively. And silicate glass’s mechanical and thermal properties were better than that of phosphate glass. But Yb3+-doped phosphate glass has lower nonlinear refraction index n2. Both Yb3+-doped silicate and phosphate glasses are possible to be used as laser medium.

Photonic nanowires directly drawn from bulk glasses

High-uniform nanowires with diameters down to 50 nm are directly taper-drawn from bulk glasses. Typical loss of these wires goes down to 0.1 dB/mm for single-mode operation. Favorable photonic properties such as high index for tight optical confinement in tellurite glass nanowires and photoluminescence for active devices in doped fluoride and phosphate glass nanowires are observed. Supporting high-index tellurite nanowires with solid substrates (such as silica glass and MgF2 crystal) and assembling low-loss microcoupler with these wires are also demonstrated. Photonic nanowires demonstrated in this work may open up vast opportunities for making versatile building blocks for future micro- and nanoscale photonic circuits and components.

Effects of non-radiative processes on the infrared luminescence of Yb 3+ doped glasses

This study is focused on the contribution of radiative and non radiative processes on the infrared emission of Yb doped phosphate glasses. The effects of energy migration and interaction with impurities, particularly OH − radicals, are discussed based on Yb 3+ luminescence and lifetime measurements. Two sets of samples with the same composition were used: one prepared at ambient conditions (set A), and the other in a dry box under N 2 atmosphere (set N). Infrared spectra have shown that OH − radicals are strongly reduced in the samples prepared in N 2 atmosphere. The Yb 3+ infrared luminescence is more intense in samples of set N by a factor 2 and small quenching is observed at least at Yb concentrations of 13%. On the other hand, the infrared emission of samples of set A is strongly quenched for Yb concentrations higher than 10%. The measured lifetimes also corroborate the conclusion that OH radicals reduce significantly the Yb 3+ fluorescence quantum efficiency.

Properties and structure of high erbium doped phosphate glass for short optical fibers amplifiers

New phosphate glasses have been developed in order to incorporate high rare-earth ions concentrations. These glasses present a great chemical stability and a high optical quality. The phosphate glass network is open, very flexible, with a linkage of the tetrahedrons very disordered and contains a larger number of non-bridging oxygens (66%). The great stability and resistance against crystallization associated with the possibility to incorporate high doping concentration of rare-earth ions in these phosphate glasses make them very good candidates for the realization of ultra short single mode amplifiers with a high gain at 1.55 μm.

Evaluation of usefulness of color digital summation radiography for detection of solitary pulmonary nodules

Optical properties of Dy3+ doped zinc phosphate glasses have been investigated. In the present study glasses with the composition xZnO · (1−x)P2O5 (0.5⩽x⩽0.7) (typical value of x=0.667) containing 0.5 mol weight of Dy2O3 are prepared. The density of the glass is determined by Archimedes’s principle and the refractive index is measured on Abbe refractometer using sodium lamp as light source. The optical absorption spectra are recorded on a Hitachi U-3400 spectrophotometer in the wavelength range 200–2500 nm. Using the Judd–Ofelt (JO) theory, the intensity parameters (Ωλ, λ=2, 4,6) have been evaluated for the glass. These intensity parameters are used to predict radiative properties that include electric (Sed) and magnetic (Smd) dipole line strengths, radiative (A) and total radiative (AT) transition probabilities, lifetimes (τR), branching ratios (βR) for the excited (6H11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2) levels of these Dy3+ doped phosphate glass.

Thermal lens study of the OH− influence on the fluorescence efficiency of Yb3+-doped phosphate glasses

In this work, the thermal lens (TL) technique is used to determine the fluorescence quantum efficiency (η) of Yb3+-doped phosphate glasses. The role of nonradiative processes such as energy migration among Yb ions and the interaction with OH− radicals are presented and discussed. Two sets of samples with the same Yb concentrations were prepared, one at ambient conditions (set A) and the other in N2 atmosphere (set N). The TL technique was shown to be very sensitive to the amount of OH radicals. Moreover, the η values obtained from the TL method are in good agreement with the calculate ones (based on lifetime measurements). The results indicate that TL can be a valuable technique to evaluate the quantum efficiency and nonradiative rates in ion-doped materials.

Kinetics of Accumulation and Decay of Paramagnetic Centers in γ-Irradiated Doped Phosphate Glasses

The dose dependences and decay kinetics of PO42− and PO32− paramagnetic centers and radiation-reduced europium Eu(3+)− in γ-irradiated phosphate glasses of composition 4Na2O · La2O3 · 7P2O5 doped with europium are studied. The data obtained are discussed within the trapping volume model in the approximation of short irradiation duration. It is shown that the trapping volume parameter v decreases with increasing irradiation dose. A physical interpretation of the parameter v is proposed.

A Compact High-Performance Optical Waveguide Amplifier

A glass waveguide amplifier was constructed in an Er/sup 3+/- and Yb/sup 3+/-doped phosphate glass. The waveguide channels were defined via a field-assisted Ag/sup +/ diffusion process. A net gain of 4.1 dB was measured at 1534 nm in a 3-mm length waveguide.

Optical and structural characterization of rare earth doped niobium phosphate glasses

Phosphate glasses containing up to 45mol% of niobium were obtained. X-ray diffraction, infrared, Raman, and optical absorption spectroscopy were used to analyze those materials. The refractive index varies from 1.70 to 1.85 as the amount of Nb increases. Niobium phosphate glasses with optical transparence in the (400–2500nm) range were produced. The cut off varied from 342nm to 378nm as a function of the Nb concentration. The cut off is due to the charge transfer O2→Nb5+. Glasses containing 10mol% of Nb2O5 are the most promising materials to be used as rare-earth ions hosts because they are chemically resistant, and show optical transparency in the spectral range of visible to infrared. Doping the glasses with 1–5mol% of Er, Ho, Pr, and Yb ions does not change the glass structure, as measured by X-ray diffraction, infrared, and Raman spectroscopy. The fluorescence lifetimes were determined for Nd, Yb, and Er, and the absorption cross-section were determined for all ions. The energy transfer in co-doped Yb–Er system was measured, and the lifetime of excited states and the luminescence efficiency were determined to be 91% for the Er 4I11/2 level, in the Yb–Er co-doped glasses.

Temperature dependence of femtosecond laser induced refractive index change in Nd3+-doped phosphate glass

We report refractive index change in a femtosecond laser irradiated Nd3+-doped phosphate glass. The effects of annealing temperature on the refractive index change of the glass have been investigated. Absorption spectra of the glass sample before and after femtosecond laser irradiation and subsequent annealing were measured. The results indicate that multiphoton absorption can undertake although there are intrinsic absorption for the glass in irradiation wavelength. The results may be useful for fabrication of three-dimensional integrated optics devices and waveguide laser devices in this glass. (c) 2004 Elsevier B.V. All rights reserved.

The Red‐Shift of Ultraviolet Spectra and the Relation to Optical Basicity of Ce‐Doped Alkali Rare‐Earth Phosphate Glasses

The ultraviolet absorption and emission spectra of Ce3+ doped phosphate glasses based on gadolinium and sodium phosphates are studied in the present work. Compared with the cerium‐free phosphate glass matrixes, CePO4 doping shifts the ultraviolet absorption edge of glasses into the longer wavelength because of the 4f–5d absorption transition of Ce3+. The emission spectra correlate such red‐shift with glass compositions. Explanations are based on variation in the optical basicity of glasses, which corresponds not only to the alkali content but also to the O/P ratio. The latter is proportional to the number of nonbridging oxygen in the oxyanion unit (PO4), and most likely plays an overwhelming role in the overall optical basicity of glasses.

Spectroscopic properties of MO-WO3-P2O5: Ho3+glasses

ESR, IR, optical absorption and photoluminescence spectra of Ho 3+ doped tungsten phosphate glasses modified with three different modifier oxides viz., PbO, ZnO and CaO have been studied. The ESR spectral studies indicate tungsten ions are present in W 5+ state in all the three glasses with the highest concentration in CaO modified glasses. From the measured intensities of various absorption bands of these glasses, the Judd-Ofelt (JO) parameters Ω2, Ω4 and Ω6 have been evaluated. The JO theory could successfully be applied to characterise the absorption and luminescence spectra of these glasses. From this theory various radiative properties like radiative transition probabilities, A, branching ratios, βr ,t he radiative lifetimes, τR, and the emission cross-sections, σ E , for various emission levels of Ho 3+ in these glasses have been determined and reported. An attempt has also been made to throw some light on the environment of Ho 3+ ions in all the three glasses. PACS. 61.43.Fs Glasses - 42.62.Fi Laser spectroscopy - 78.40.pg Disordered solids

Temperature-dependent stimulated-emission cross section and concentration quenching in Nd^3+-doped phosphate glasses

Measurements are reported of the spectroscopic properties of phosphate glasses doped with 3-, 5-, and 10-wt. % Nd3+ in the temperature range 70–300 K. The stimulated-emission cross sections of these glasses were determined by use of the Füchtbauer–Ladenburg formula at each temperature. The absorption spectra at room temperature were used to calculate the 4F3/2→4I11/2 stimulated-emission cross section and the 4F3/2 radiative lifetime according to Judd–Ofelt theory. Good agreement was obtained between measured and calculated stimulated-emission cross sections at room temperature. As the temperature decreased, the emission cross section increased while the emission lifetime remained constant for all the samples. The temperature dependences of the stimulated-emission cross sections for the differently doped glasses are in good agreement with earlier predictions.

Controllable precipitation and dissolution of silver nanoparticles in ultrafast laser pulses irradiated Ag+-doped phosphate glass

We report a controllable process of recipitation and dissolution of silver nanoparticles in ultrashort laser pulses irradiated Ag+-doped phosphate glass. Absorption spectra, transmission electron microscopy and refractive index measurement revealed that metallic silver nanoparticles were precipitated in the glass sample after irradiation by an 800-nm femtosecond laser and subsequent annealing at 300 degrees C, and dissolved after further annealing at 450 degrees C. We discuss a mechanism that combines the formation and decoloration of color centers, precipitation and dissolution of silver nanoparticles.

Ultraviolet transparency and activator oxidation state of Ce3+-doped phosphate glasses

A set of Ce3+ activated phosphate glasses is studied. Dependence of the absorption band-edge position on the activator content and glass composition is discussed with respect to variation of the so-called optical basicity. XPS analysis of the samples is performed to get information about the oxidation state of the Ce activator cations in the glasses.

Cooperative luminescence in Yb3+-dopedphosphate glasses

In this paper we present results on cooperative luminescence performed on Yb3+-dopedmetaphosphate glasses under 980 nm excitation. We have measured emissionspectra and decay lifetimes in the visible and infrared regions as afunction of Yb concentration. It was observed that, up to 10% of Ybconcentration, cooperative emission increases while lifetime is observed todecrease. Such behaviour is attributed to the Yb interaction with OH−radicals and energy migration among Yb ions.