Nonlinear optical characterization of phosphate glasses based on ZnO using the Z-scan technique

The nonlinear optical properties of a phosphate vitreous system [（ZnO）x-（MgO）30-x-（P2O5）70], where x=8, 10, 15, 18, and 20 mol% synthesized through the melt-quenching technique have been investigated by using the Z-scan technique. In the experiment, a continuous-wave laser with a wavelength of 405 nm was utilized to determine the sign and value of the nonlinear refractive （NLR） index and the absorption coefficient with closed and opened apertures of the Z-scan setup. The NLR index was found to increase with the ZnO concentration in the glass samples by an order of 10-10 cm2·W-1. The real and imaginary parts of the third-order nonlinear susceptibility were calculated by referring to the NLR index （n2） and absorption coefficient （β） of the samples. The value of the third-order nonlinear susceptibility was presented by nonlinear refractive or absorptive behavior of phosphate glasses for proper utilization in nonlinear optical devices. Based on the measurement, the positive sign of the NLR index shows a self-focusing phenomenon. The figures of merit for each sample were calculated to judge the potential of phosphate glasses for application in optical switching.

Optical properties of phosphate glasses co-doped with Yb^(3+) and silver nanoparticles

We report the fabrication and spectroscopic characterization of Yb^3＋-doped phosphate glass, also containing silver nitrate. Scanning electron microscopy（SEM） provides the evidence of the formation of silver nano-particles（SNPs）, which are formed as a consequence of melting and thermal decomposition of Ag NO3. Absorption spectra of the samples in the visible-to-near-infrared spectral range reveal the presence of bands centered at 410 nm associated with the SNP-plasmon resonance, and at 976 nm due to the Yb^3＋. Under 916-nm laser-diode pumping, the effect of the SNP reflects that： i） the fluorescence in the 950-nm–1150-nm spectral range is strongly enhanced（～ 30 times）, while the fluorescence decay time associated with the ^2F5/2→^2F7/2transition of Yb^3＋ increases 25%, and ii） the basic lasing properties（saturation pumping intensity, the emission and absorption cross sections） are substantially improved.

Energy transfer from Ce^(3+) to Tb^(3+) and Eu^(3+) in zinc phosphate glasses

Ce3+,Eu3+ and Tb3+ singly doped and Ce3+/Eu3+ and Ce3+/Tb3+ co-doped zinc phosphate glasses were prepared by sintering P2O5,ZnO,Ce2(C2O4)3·10H2O and Eu2O3/Tb4O7 mixtures at 1200 °C in the air for 2 h and then annealing at 450 °C for 10 h.The obtained glasses were homogeneous and transparent.The glasses without Ce3+ were colorless and those with Ce3+ showed slightly yellow.The singly doped glasses showed strong emissions and excitations from doped trivalent rare earth ions.Strong energy transfer from Ce3+ to...

Spectral and Lasing Properties of Er^(3+0/Yb^(3+) Co-Doped Phosphate Glasses Pumped by LD

Er^3 ＋/Yb^3 ＋ phosphate glasses were fabricated. According to McCumber theory, the stimulated emission cross-section of Er^3＋ ions at 1533 nm was calculated on the basis of absorption spectrum, and 0.84 × 10^-20 cm^2 is derived, the fluorescence lifetime of ^4I13/2 level is 8.5 ms. An Er^3＋/Yb^3＋ co-doped phosphate glass CW laser pumped by LD was demonstrated at room temperature. The maximum output power is 80 mW and slope efficiency is 16.5%.

Effects of Zn/P ratio on structures and properties of zinc-iron phosphate glasses

Effects of Zn/P ratio on the structures and properties of glasses with the general composition of （80-x）ZnO-20Fe2O3-xP2O5 （x=40, 45, 50, 55, 60） （molar fraction, %） were investigated. Glass structure was measured by infrared absorption spectrum. Glass density （/9） was measured by the Archimedes method. Coefficients of thermal expansion （a） and characterization temperature were obtained by a dilatometer. Water durability of each glass was estimated from the dissolution rate （DR）in water at 90 ℃ for 24 h. With increasing Zn/P ratio, water durability of zinc-iron phosphate glasses increases dramatically without large increase in the characterization temperature. （80-x）ZnO-20Fe2O3-xP2O5 glasses with 0.3≤Zn/P≤0.5 are suit for low-to-mid temperature sealing application for substrates with a〈8.0× 10^-6℃^-1.

Red Long Lasting Phosphorescence of Mn^(2+) Doped Zinc Phosphate Glasses

Mn^2＋ doped ZnO-P2O5 glasses emit red fluorescence, which shows that Mn^2＋ ion doped in zinc phosphate glass is octahedrally coordinated. Moreover, glass samples exhibit bright red long lasting phosphorescence （LLP） when the mole percent of ZnO are more than 60%. After turnoff the irradiation source of UV lamp peaking at 254 nm, the red phosphorescence can be observed for about 6 h in the limit of light perception for naked eyes （0.32 mcd/m^2）. Photoluminescence （PL） spectra, LLP emission spectra and decay curves were detected. Increasing MnO or ZnO content, the phosphorescence intensity can be improved distinctly and the emission wavelength can be also adjusted from 595 nm to 628 nm. According to the structural characteristic of zinc phosphates glasses, we suggest that non-bridge oxygen （NBO） is probably related with the arising of LLE Meantime, the variation of crystal field intensity induced that the LLP emission wavelength red shifts.

Effect of Network Modifiers on Spectroscopic Properties of Erbium-doped Phosphate Glasses

The integrated absorption cross section Σ abs, peak emis sion cross section σ emi, Judd-Ofeld intensity parameters Ω t(t=2,4,6), and spontaneous emission probability A R of Er 3+ ions were determined fo r Erbium doped alkali and alkaline earth phosphate glasses. It is found the comp ositional dependence of σ emi is almost similar to that of Σ abs, wh ich is determined by the sum of Ω t (3Ω 2+10Ω 4+21Ω 6). In addition, the compositional dependence of Ω t was studied in these glass systems. As a resu lt, compared with Ω 4 and Ω 6, the Ω 2 has a stronger compositional depend ence on the ionic radius and content of modifiers. The covalency of Er-O bonds in phosphate glass is weaker than that in silicate glass, germanate glass, alumi nate glass, and tellurate glass, since Ω 6 of phosphate glass is relatively la rge. A R is affected by the covalency of the Er 3+ ion sites and correspon ds to the Ω 6 value.

Preparation and Thermal Stability of Phosphate System Protection Glasses Doped with Rare Earths

The formation ability and thermal stability of phosphate laser protection glass doped with high Sm2O3 content were discussed. The characteristic temperatures ( Tg, Tc, Tm) were measured by DSC and the crystallization parameter β was calculated. The results show that the forming regions would shrink and tend to closed ellipse with increasing of Sm2O3 content. Increasing of BaO/Al2O3 ratio changes the network structure of rare earth glass and improves the thermal stability finally. However, with the increasing of Sm2O3 content, the β increases firstly and then decreases, and finally the thermal stability also increases firstly and then decreases.

Local structure and luminescent properties of lead phosphate glasses containing rare earth ions

Local structure and luminescent properties of lead phosphate glasses containing rare earth ions were studied. Optically active ions such as Eu^3＋, Dy^3＋, Tb^3＋ and Er^3＋ were chosen as dopants. The local structure was verified using X-ray diffraction and Fourier transform inflared （FT-IR） spectroscopy. The visible luminescence bands recorded for the studied samples corresponded to ^5D0→^7Fj （J=0÷4） transitions of Eu^3＋, ^4F9/2→^6Hj/2 （J=11÷15） transitions of Dy^3＋, ^5D3→^7FJ, （J＇=1÷6） and ^5Da→^7FJ （J=3÷6） transitions of Tb^3＋, and ^4S1/2→^4I15/2 transitions of Er^3＋.

The influence of OH groups on laser performance in phosphate glasses

Because of the influence of OH groups in phosphate glasses on the radiation of rare-earth ions, the laser performance is degraded. The laser efficiency and the small signal gain experiment of several phosphate glass samples have been done, the concentration of OH groups in glasses was calculated from the measured absorption coefficient at 3.47 μm. It is shown that the concentration of OH groups in phosphate glasses can seriously influence the laser output characteristics, and the OH groups have worse influence on the laser amplifier than laser oscillator.

Structural and optical studies of Yb^(3+),Er^(3+) and Er^(3+)/Yb^(3+) co-doped phosphate glasses

Phosphate glass samples with various Yb2O3 and Er2O3 contents were synthesized by the conventional melt quenching technique and characterized by X-ray diffraction, IR absorption spectroscopy and Raman scattering spectroscopy. The absorption, emission spectra and fluorescence decay studies were carried out both at low and room temperatures. Results showed the existence of several sites occupied by the rare earth ions in the phosphate glass. Up-conversion and cooperative fluorescence were also discussed.

Cooperative energy transfer in Tm^(3+)and Yb^(3+) co-doped phosphate glasses

An efficient near-infrared （NIR） quantum cutting （QC） in Tm3＋ and Yb3＋ co-doped phosphate glasses was demonstrated, which involved the emission of two NIR photons from an absorbed visible photon via a cooperative energy transfer （CET） from Tm3＋ to Yb3＋ ions. Judd-Ofelt （J-O） theory was used to calculate the intensity parameters （ 2 , 4 , 6 ）, the radiative transition rates （Ar ）, and radiative transition lifetime （τ rad ） of Tm3＋ . Based on Inokuti-Hirayama＇s model, the energy transfer processes were studied and results indicated that the energy transfer of the electric dipole-dipole （Edd） was dominant in this system. Quantum efficiency related to Yb 3＋ concentration was calculated, and the maximum QE efficiency reached 169.8%.

Luminescent Properties and Energy Transfer Mechanism of Gd^(3+) and Eu^(2+) Co-doped Phosphate Glasses

The phosphate glasses doped with Eu2＋, Gd3＋, respectively, and co-doped with Gd3＋ and Eu2＋ were prepared by high-temperature melting method. The transmission spectra, the excitation spectra, the emission spectra and the fluorescent decay time were investigated. The energy transfer process between Gd3＋ and Eu2＋ was studied. From the excitation spectra and the emission spectra of the phosphate glasses doped with Eu2＋, we observed that the emission intensity of Eu2＋ shows higher for 0.02 mol% Eu2＋-doped phosphate glass. According to the excitation spectra and the emission spectra and the fluorescence decay curves, when the concentration of Eu2＋ was 0.02 mol%, the optimal con- centration of Gd3＋ was 0.3 tool%. Based on Dexter theory, it is shown that the energy transfer between Gd3＋ and Eu2＋ was nonradiation energy transfer by analyzing the energy-level diagram. The fluorescence decay curves of Gd3＋ were expressed by the Inokuti-Hirayama＇s model and were used to analyze energy transfer mechanism between Gd3＋ and Eu2＋. And the energy transfer efficiency was also calculated.

Silver nanoparticles enhanced near-infrared luminescence of Er^3＋/Yb^3＋ co-doped multicomponent phosphate glasses

A new way to improve the 1.53μm emission in Er3＋/Yb3＋ co-doped multicomponent phosphate glass was demonstrated by introducing silver nanoparticles （NPs） in rare-earth doped glass. The existence of Ag NPs was confirmed by absorption spectra and transmission electron microscopy （TEM） measurements. The homogeneous distribution of silver NPs could be observed by the TEM images. UV-Vis-NIR absorption spectra revealed that the surface plasmon band was centered at about 420 nm. The photoluminescence spectra of glass samples were used to investigate the effect of silver NPs on the fluorescence properties of Er3＋. Efficient 1.53μm emis-sion was obtained in prepared samples when pumped at 980 nm laser diode （LD）. The 1.53μm emission intensity could be enhanced 87% by doping 2 mol.% AgCl due to the increased localized field effect in the vicinity of NPs and the possible energy transfer from silver NPs to Er3＋ions. Our present work may point out one way to enhance the gain coefficient of Er3＋/Yb3＋ co-doped glass fiber.

Guiding properties of proton-implanted Nd^(3+)-doped phosphate glass waveguides

We report on the fabrication and properties of an optical waveguide in Nd^(3+)-doped phosphate glass.The planar waveguide was obtained by 550-ke V proton implantation with a dose of 8.0×10^(16)ions/cm^(2).The proton–glass interaction was simulated by the stopping and range of ions in matter(SRIM software).The characteristics of the waveguide including the refractive index profile and the near-field intensity distribution were studied by the reflectivity calculation method and the end-face coupling technique.The optical waveguide demonstrated multi-mode behavior at the wavelength of 632.8 nm.The propagation features of the proton-implanted Nd^(3+)-doped phosphate glass waveguide shows its potential to operate as an integrated photonic device.

Chemical Durability, Structure Properties and Bioactivity of Glasses 48P<SUB>2</SUB>O<SUB>5</SUB>-30CaO-(22−x)Na<SUB>2</SUB>O-xTiO<SUB>2</SUB>(With 0 <x ≤ 3;mol%)

Phosphate glasses of composition 48P2O5-30CaO-(22−x)Na2O-xTiO2 (with 0 < x ≤ 3, mol%) were prepared by direct melting at 1080°C ± 20°C. The chemical durability of these glasses shows an improvement when the TiO2 content varies from 0 to 2 mol%. The measurements of differential thermal analysis and density, both, indicate the increase of the glass transition temperature and the density. The increase of Tg leads to an improvement of glass rigidity. X-ray diffraction analysis of the glasses annealed at 650°C for 48 h, indicates the appearance of a mixture of metaphosphate and pyrophosphate phases when the TiO2 content varies from 0 to 2 mol%, the last become majority when the TiO2 content rich 2 mol%. Nevertheless, when the TiO2 content exceeds 2 mol%, the analysis, both, by infrared spectroscopy and X-ray diffraction, reveals a radical change of structure with the formation of majorities isolated orthophosphate groups. SEM micrographs illustrated that the number of crystallites increased in the glass network when the TiO2 content increased at the expense of the Na2O content. An increase in the TiO2 content beyond 2 mol% led to the formation of a larger number of crystallites of different sizes, dominated by small crystallite sizes assigned to majority isolated short orthophosphate groups. This phenomenon led to a decrease in chemical durability and seems to be the main cause promoting the bioactivity of glasses. The results of the bioactivity, after a test in an SBF physiological solution within 15 days, shows, both, the formation of hydroxyapatite and tricalcium phosphate layers, in addition to the layer Ca2P2O7, known by its bioactivity, in some samples. The results obtained on the glasses studied make them potential candidates for an application in tissue engineering.

Preparation and Spectra Properties of BaO-Al_2O_3-P_2O_5-Sm_2O_3 System Protection Glasses

The forming-regions of phosphate glasses doped with high Sm2O3 contents were studied by two step melting method. The relationship between absorption spectrum and rare earth contents was also discussed. The spectra of BASP glasses were measured by spectrophotometer. The results show that the forming regions will shrink with the increase of Al2O3 and it is difficult to form glass when [PO4]/[AlO4] < 2. The forming regions tend to be a closed elliptical, and the intensity of characteristic absorption peak increases gradually with the increase of Sm2O3, the absorption lines broadens non-uniformly and there is approximate linear relation between optical density at the 1064 nm wavelength and Sm2O3 content.

Phosphate Glass Fibre Composites for Bone Repair

We investigate high-modulus degradable materials intended to replace metals in biomedical applications.These are typically composites comprising a polylactide(PLA)matrix reinforced with phosphate glass fibres,which provide reinforcement similar to E-glass but are entirely degradable in water to produce,principally,calcium phosphate.We have made composites using a variety of fibre architectures,from non-woven random mats to unidirectional fibre tapes.Flexural properties in the region of 30 GPa modulus and 350 MPa strength have been achieved-directly comparable to quoted values for human cortical bone.In collaboration with other groups we have begun to consider the development of foamed systems with structures mimicking cancellous bone and this has shown significant promise.The fibres in these foamed structures provide improved creep resistance and reinforcement of the pore walls.To date the materials have exhibited excellent cellular responses in vitro and further studies are due to include consideration of the surface character of the materials and the influence of this on cell interaction, both with the composites and the glass fibres themselves,which show promise as a standalone porous scaffold.

Crystallization Kinetics of Lithium Aluminum Germanium Phosphate Glass by DSC Technique

Abstract： The crystallization kinetics of Li20-A12O3-GeO2-P205 （LAGP） glass fabricated via the conventional melt-quenching method was studied by differential scanning calorimetry （DSC） under non- isothermal condition at different heating rates. The activation energy of glass transition Eg is 634.4 kJ/mol, indicating that LAGP glass is easy to crystallize at an elevated temperature. The activation energy of crystallization Eo and Avrami index n obtained from Matusita＇s model are 442.01 kJ/mol and 1.7, respectively. The value of n reveals that bulk crystallization predominates slightly over surface crystallization during crystallization process. LAGP glass-ceramics after different heat treatments have the same crystalline phases determined as major phase LiGe2（PO4）3, with A1PO4 and GeO2 as their impurity phases.

Fusion Splicing Experiments of 1060-XP Silica Fiber with Phosphate Glass Fiber

An asymmetric heating method for fusion splicing of 1 060-XP silica fiber （1 060F） and phosphate glass fiber （PGF） using an electric arc splicer has been proposed. Double joints with the lowest splice loss of 0.6 dB and good bending-resist strength between 1 060 F and PGF has been obtained. The main reasons affecting fiber splice loss and strength have been analyzed.