Co-doped Fluorophosphate Glasses Research Articles

Enhancing light output of WSLED with microlens array fabricated on Tb³⁺/Sm³⁺ co-doped fluorophosphate glass via hot embossing

In this study, Tb3+/Sm3+ co-doped NaPO3–BaF2–AlF3–CaF2 glasses were synthesized using the melt quenching method. These glasses exhibit a glass transition temperature below 380 °C and maintain optical transparency close to 90% within the visible spectrum. Furthermore, under UV excitation, the emission shows a wide spectrum and varies with the rare-earth doping ratio or excitation wavelength. Hence, this glass was introduced into the wide-spectrum light-emitting diode (WSLED) application. Moreover, a microlens array was fabricated on the glass surface using the hot embossing technique. In fact, the microlens array enhanced the light output power of the WSLED by 5% at a driving current of 150 mA.

Structural environment influence on Faraday effect in Tb3+ and Pr3+ co-doped fluorophosphate glass and glass-ceramics containing TbOF nanocrystals

The influence of structural environment of lanthanide ions on the co-doping Faraday effect is explored within fluorophosphate glasses and glass ceramics. In a first part, the crystallization process of a glass with a nominal composition 35 NaPO3 – 15 BaF2 – 50 TbF3 is explored in function of duration and temperature of the ceramization process. X-ray diffraction analysis and STEM-HAADF allowed the identification of crystalline TbOF cubic fluorite phase in these glass-ceramics, with a maximum crystalline fraction of 42 ± 2 wt% for a crystallite size of 46 nm for the sample heat-treated 10 h at 394 °C. In a second part, TbOF glass-ceramics following the composition law 35 NaPO3 – 15 BaF2 – 0.5 ((100-x) TbF3 – x PrF3) with x = 0, 1, 2, 3, 4 and 5 are prepared at the optimal heat treatment of 10 h at 394 °C corresponding to maximal crystalline fraction and optical transmission. The Verdet constants of these co-doped glass-ceramics are characterized and compared to the ones of the parent glasses. The maximum co-doping efficiency reaches 1.075 for the glass-ceramic, compared to a value of 1.037 for the corresponding co-doped glass samples. The structural organization around the lanthanide cation site increases the co-doping influence on the Faraday Effect by optimization of the superexchange interaction.

Near-IR luminescence at 1.06 μm of Nd3+-Pr3+ co-doped lithium fluorophosphate (LFP) glasses

We report experimental investigations into the co-doping of Nd3+-Pr3+ ions in LFP glasses. The method used in this study is the melt quench technique. Several physical and structural properties were investigated in this work. The structural properties were investigated by FTIR (Fourier Transform infrared) and XANES (X-ray absorption near edge structure) spectroscopy. The location of the white line peak at ∼6210 eV and the intensity of L3-edge XANES of Nd depend on the ratio of O/Nd in the glass matrix. Several excitations exhibited the luminescence properties in the photo and near-infrared spectrophotometer. The excitation at 481 nm shows seven peaks in the Nd3+ and Pr3+ transitions in the visible region. Meanwhile, the near-infrared region shows three peaks of Nd3+ and Pr3+ transitions at ∼1.06 μm wavelength.

Enhancement of the radiation resistance of cerium-containing fluorophosphate glasses through codoping with Sb2O3 and Bi2O3

The growing demand for radiation-resistant optical glasses for space and nuclear radiation applications has attracted significant research interest. However, radiation-resistant fluorophosphate glasses have been poorly studied. In this work, we report on the tailoring and performance of radiation-resistant fluorophosphate glasses that contained cerium through codoping with Sb2O3 and Bi2O3. The physical properties, optical properties, microstructure, and defects of fluorophosphate glasses were investigated using transmittance measurements, absorption measurements, as well as Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) spectroscopy. The results showed that the radiation resistance of all codoped fluorophosphate glasses was better than the undoped cerium-containing fluorophosphate glasses after 10–250 krad(Si) irradiation. Especially in glasses doped with Bi2O3, the optical density increment at 385 nm was only 0.1482 after 250 krad(Si) irradiation. The CeO2 prevented the development of phosphate-related oxygen hole center (POHC) defects, whereas further codoping with Bi2O3 suppressed the formation of oxygen hole center (OHC) and POEC defects, reducing the breaking of phosphate chains caused by CeO2. Bi3+ is more likely than Sb3+ to change the valence, affecting the transition equilibrium of intrinsic defects and reducing the concentration of defects produced by irradiation. When codoping with Sb2O3 and Bi2O3, Bi2O3 does not enhance radiation resistance owing to the scission effect of Sb2O3 on the phosphate chain, which is not conducive to the radiation resistance of glasses. This indicates that the cerium-containing fluorophosphate glasses doped with Bi2O3 can effectively suppress the defects caused by irradiation and improve the radiation resistance of the glasses.

Energy transfer and broad-band luminescence of Nd3+-Er3+ co-doped Lithium Fluorophosphate (LFP) glasses

Nd3+-Er3+co-doped lithium fluorophosphate (NdEr) glasses with broad-band emission were made by the traditional melt quenching technique. These glasses were characterized through physical, absorption spectra, NIR luminescence properties and structural studies using XANES. The absorption spectra of this work showed an increase with the increasing concentration of Er2O3 in the glass. The Near-Infrared (NIR) luminescence spectra were obtained from several excitation sources. The energy level diagram studied the interraction process and energy transfer mechanism. The emission intensity of Er2O3 increases up to 1.5 mol%, the concentration quenching effect makes the emission 4F3/2 → 4I9/2, 4I11/2 and 4I13/2 Nd3+ intensity weaken, which means Nd3+→Er3+ energy transfer enhanced. The Judd-Ofelt (JO) theory investigations have been applied for Nd3+ ions and found that the trend follows Ω6>Ω4>Ω2. The stimulated emission cross-section is calculated in two ways: F u¨ chtbaueer Ladenburg (FL) method and Mc-Cumber theory. The decay time is found to be bi-exponential when monitored at λex = 581 nm and λem = 1061 nm. The XANES spectra of Nd LIII-edge were investigated and the absorption band showed at ∼6209.8 eV, confirming the presence of Nd3+. The XANES spectra of Er LIII-edge were investigated and the absorption band showed at ∼8362.5 eV, confirming the presence of Er3+.

Synthesis and structural characteristic of Nd3+/Er3+ co-doped Lithium Fluorophosphate (LFP) glasses

Transparent fluorophosphate glass containing face center cubic LiF crystals doped with Nd3+/Er3+ were succesfully characterized by melt-quenching method. The sample composition following chemical formula (65-x)P2O5-20LiF-14CaF-1Nd2O3-xEr2O3 (x = 0.0; 0.5; 1.0; 1.5 and 2.0 mol%). The density parameter was calculated using Archimedes method in distilled water and this value used to calculating of molar volume. Several physical properties of Nd3+/Er3+ co-doped LFP glasses were calculated and correlated with structural properties. The X-ray diffraction (XRD) spectrum used to verify the glasses structure. The further structural characteristic was investigated using FTIR. Based on the investigation is discovered that the prepared co-doped glasses shows amorf and high transparency.

Structural Environment Influence on Faraday Effect in Tb3+ and Pr3+ Co-Doped Fluorophosphate Glass and Glass-Ceramics Containing Tbof Nanocrystals

Structural Environment Influence on Faraday Effect in Tb3+ and Pr3+ Co-Doped Fluorophosphate Glass and Glass-Ceramics Containing Tbof Nanocrystals

Near-Ir Luminescence at 1.06 Μm of Nd3+-Pr3+ Co-Doped Lithium Fluorophosphate (Lfp) Glasses

Near-Ir Luminescence at 1.06 Μm of Nd3+-Pr3+ Co-Doped Lithium Fluorophosphate (Lfp) Glasses

Upconversion luminescence and energy transfer in the fluorophosphate glasses with low phosphate content doped with Tm3+ and Yb3+ions

We report an experimental observation of the upconversion in fluorophosphate glasses doped with different concentrations of Tm 3+ ions (from 10 20 to 10 15 ion/cm 3 ) and a constant content of Yb 3+ ions (10 21 ion/cm 3 ) when pumped by a diode laser with a wavelength of 975 nm with a change in the pumping power density from 2.0 to 14.5 kW/cm 2 . Possible mechanisms of population of the upper 1 D 2 , 2 G 4 and 3 F 2,3 states of Tm 3+ ions were discussed depending on their concentration. The role of cross-relaxation processes in the population of the upper excited levels is considered. A change in the values of n -parameter of the luminescence at 475 nm ( 1 G 4 ) from 3 to 2 and high upconversion at low Tm 3+ ions concentrations (about 10 18 -10 15 ion/cm 3 ) were attributed to the cooperative energy transfer from Yb-Yb* dimers. It was found that Tm 3+ /Yb 3+ co-doped fluorophosphate glasses could be promising as up-converting materials. • The concentration dependence of the UC luminescence of Tm 3+ /Yb 3+ co-doped fluorophosphate glasses was studied. • Mechanisms of population of the state 2 D 1, 3 F 2,3 , 1 G 4 and 1 P 0 of Tm 3 + ions were discussed depending on their concentration. • The cooperative energy transfer from Yb-Yb* dimmers led to the high upconversion at low Tm 3+ ions concentrations.

NIR and visible luminescence of Er3 +/Yb3+ co-doped fluorophosphate glasses with small additives of phosphates

A series of new fluorophosphate glasses co-doped with Er3+/Yb3+ions with composition 5 Ba(PO3)2–(90-x)(AlF3 –CaF2 –MgF2 –BaF2–SrF2)–5YbF3-xErF3, where x = 0, 0.1, 0.5, 1.0, 2.0, 3.0, 5.0 (mol.%) were developed. Impact of the Er3+ ions concentration on the luminescent properties was studied. Using Judd-Ofelt theory phenomenological intensity parameters Ωt (t = 2; 4; 6) were obtained. The stimulated emission cross-sections of 4I13/2→4I15/2 transitions were determined by the Fuchtbauer-Landenburg equation (FL) and the modified reciprocity method (MR). The upconversion spectra were measured as a function of the power density in the range 1.8–12.4 kW/cm2 and temperature in the range from 293 K to 693 K. It was found that the high intensity of UC luminescence of Er3+ ions and impurity Tm3+ ions occurs by the mechanism cooperative energy transfer (CET), which means the formation of excited clusters (dimers) of ytterbium. The sensitivity and temperature of the maximum sensitivity were evaluated by the fluorescence intensity ratio method from the measured up conversion spectra. The maximum value of absolute thermal sensitivity Smax of 40 × 10−4 K−1 at 693 K was obtained for the sample doped with 0.5 mol % of ErF3.

Energy transfer induced enhancement in NIR luminescence characteristics of Yb3+/Er3+ co-doped sodium zinc bismuth fluorophosphate glasses

The results pertaining to the energy transfer-based photoluminescence characteristics of Er3+-doped and Yb3+/Er3+ co-doped NaF–ZnO–BiF3–NH4H2PO4 (NZBFP) glasses prepared through melt-quench technique were demonstrated here. By applying McCumber's theory, the absorption, stimulated emission cross-sections and optical gain have been estimated for Yb3+ (0.97 μm) and Er3+ (1.54 μm) ions. Yb3+-doped glass exhibited a sharp emission at 979 nm at 808 nm excitation while Er3+-doped glass displayed a broad NIR emission band at/around 1545 nm for 980 nm excitation. The presence of Yb3+ absorption band along with the Er3+ absorption bands in the co-doped glass suggests the energy transfer (ET) possibility within these ions. On pumping Er3+-doped &yYb3+/Er3+ co-doped NZBFP glasses with 980 nm Laser Diode, a broad Er3+ emission at 1545 nm attributed to 4I13/2 → 4I15/2 is observed in the NIR region. The increasing of Yb3+concentration with respect to Er3+ (fixed to 1 mol%) in co-doped glasses have resulted in enhancement of Er3+ NIR emission because of the resonant energy transfer (ET) process from Yb3+→Er3+. The energy transfer (ET) mechanism has been illustrated from the spectral overlap of Yb3+ emission and Er3+ absorption, Er3+ decay lifetime curves, and partial energy level diagram. Further, the nature of interaction responsible for the energy transfer process (ET) has been explained using Forster-Dexter theory and I–H fitting. In addition, the suitability of the present synthesized fluorophosphate glasses for optical amplifier and NIR laser applications were explored in terms of optical amplification and gain parameters, like effective band-width (Δλeff), stimulated emission cross-section (σe), optical gain (G), and gain bandwidth (ΔG).

Synthesis and characterization of Er3+/Cu+-codoped fluorophosphate glasses

NaPO3-ZnF2 binary fluorophosphate glasses doped with trivalent erbium and monovalent copper were synthesized by the conventional melting and casting method using ErF3 and CuCl as starting materials. The samples were systematically investigated using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. X-ray powder diffraction patterns confirmed that the as-prepared compounds were all amorphous. The glass transition temperature (Tg) was observed around 230 °C by DSC analysis, while the thermal stability range (ΔT) was estimated to be between 90 and 140 °C. The measured value of the refractive index (n) was measured as 1.502 at a wavelength of 632.8 nm. Thermal annealing of the samples was performed at different temperatures above Tg for various heat-treatment times. During these steps, monovalent copper and sodium ions were expected to be reduced, forming metallic nanoparticles. This transformation lead to coloration changes, depending on the annealing time and temperature, with respect to the transparency of the glasses. These spectroscopic changes are related to the plasmonic effects induced by the presence of both Cu and Na metallic nanoparticles, which promote red shift due to absorption. The VIS-NIR absorption spectra of the prepared glasses were investigated in the frame work of standard Judd-Ofelt (J-O) theory, which was used to determine the J-O intensity parameters, radiative transition probabilities and branching ratios for Er3+ ions embedded in the glasses. The calculated intensity parameters (Ω2,4,6) were compared to those obtained for Er3+ in several other glasses.

Spectroscopic properties of Er3+/Yb3+ co-doped fluorophosphate glasses for NIR luminescence and optical temperature sensor applications

A series of Er3+/Yb3+ co-doped fluorophosphate glasses with varying YbF3 concentration were prepared by a high temperature melt quenching technique. Absorption and emission cross-sections were determined by using the McCumber theory. The larger emission cross-section (9.86×10−21cm2) and longer fluorescence lifetime (12.37ms) were obtained for the 4I13/2→4I15/2 transition of ABS3Er4Yb glass. The sensitivity and temperature of the maximum sensitivity were evaluated by the fluorescence intensity ratio method from the measured upconversion spectra. The results were discussed and compared to the other reported glasses.

Highly efficient and tunable white light emission of Sn2+-Dy3+ co-doped fluorophosphate glasses

A series of Sn2+-Dy3+ co-doped fluorophosphate glasses (FPGs) were prepared by the melt quenching method. The luminescent properties and energy transfer mechanisms of the FPGs glasses were investigated through photoluminescence and decay lifetime analysis. By controlling the concentration of Dy3+, the FPGs present a white light with a CIE chromaticity coordinate of (0.311, 0.330), which is very close to the standard equal energy white light illumination. The corresponding quantum efficiency, CRI and the brightness are 56.3%, 75 and 6706 cd/m2, respectively. Furthermore, the physical and chemical stability and thermal properties were also analyzed using differential scanning calorimetry and a thermal conductivity detector. The corresponding values of the ∆T (Tx-Tg) and thermal conductivity are 155 °C and 3.02~3.31 W/m·K, respectively. These results demonstrate that the FPGs can be a promising candidate for tunable white light phosphors.

Efficient 2 μm emission and energy transfer mechanism of Ho3+ doped fluorophosphate glass sensitized by Er3+ ions

Fluorophosphate glass co-doped with Er3+ and Ho3+ ions has been synthesized by high temperature melting method. Using a commercially available 980 nm laser diode, intense about 2 μm emissions were successfully obtained in present Ho3+/Er3+ co-doped glasses without obvious quenching. To understand 2 μm fluorescence behaviors of the prepared glasses, 1.55 μm emission spectra, energy transfer mechanism and microparameters from different levels of Er3+ to Ho3+ ions have been obtained and discussed. As a result, the Er3+/Ho3+ co-doped fluorophosphate glass with excellent spectroscopic properties might be appropriate host material for 2 μm solid laser.

Thermal stability and spectroscopic study of Ho3+/Yb3+ co-doped fluorophosphates glasses

Holmium/Ytterbium co-doped fluorophosphate glasses with compositions (80-x-y) NaPO3-10SrF2-10ZnF2- xHoF3- yYbF3 (x = 1 and y = 0.5, 1, 1.5 and 2 mol%) were prepared by melt-quenching technique. The stability criteria indicate that these glasses exhibit a good resistance against devitrification. Densities of glasses were determined and showed an almost linear variation with increase of YbF3 content. Spectroscopic parameters of Ho3+ such as radiative transition probability, branching ratio, spectroscopic quality factor, integrated emission cross section and radiative lifetime, were calculated on the basis of Judd-Ofelt analysis. The results showed that these glasses could be proposed as suitable lasing materials.

Longer lifetime of Er3+/Yb3+ co-doped fluorophosphate glasses for optical amplifier applications

Er3+/Yb3+ co-doped fluorophosphate glasses with the molar composition of Mg(PO3)2-(50-x)BaF2-CaF2:3ErF3/xYbF3, where x=3, 4, 5, 6, 7, 8 and 9mol%, were prepared by a conventional melt quenching technique and studied their spectroscopic properties for fiber amplifier applications. The strong emission band at 1.53μm corresponding to 4I13/2→4I15/2 transition of Er3+ ion was observed for all the studied glasses and found the optimized Er/Yb concentration of 3:4. The emission cross-section of 1.53μm emission band was calculated to be of the order of 2.60×10−20cm2 by using the McCumber theory. The effective bandwidth was found to be of the order of 84 nm. To the best of our knowledge, for the first time, longer excited state lifetime (t=~15ms) for the 4I13/2 level of Er3+ ion was noticed for the optimized Er3+/Yb3+ co-doped fluorophosphate glasses. Those results were compared to the other host matrices and found that the investigated fluorophosphate glasses are promising and attractive as gain media for laser and fiber amplifier applications.

Analysis of structure origin and luminescence properties of Yb3+–Er3+ co-doped fluorophosphate glass

The near infrared luminescence properties of Yb(3+)-Er(3+) co-doped fluorophosphate glasses have been investigated. The various effects on structure and 1.53 μm emission were analyzed as a function of Yb(3+) concentration. The energy transfer mechanism was proposed. High measured lifetime (10.75 ms), large effective full widths at half maximum (73.71 nm) and large gain per unit length (62.8 × 10(-)(24)cm(2)s) have been achieved in prepared glass. The present glass co-doped with 6mol% YbF3 and 2 mol% ErF3 showed magnificent luminescence properties for telecommunication application.

Ho3+ doped fluorophosphate glasses sensitized by Yb3+ for efficient 2 μm laser applications

In this paper, new Ho3+/Yb3+ co-doped fluorophosphate glasses with superior thermal stability against crystallization have been synthesized. Intense 2μm emissions have been observed when pumped by a conventional 980nm laser diode. High infrared transmittance (82%) and low hydroxyl concentration (16.7ppm) can be realized according to the analysis of infrared transmittance spectrum. Based on the measured absorption spectra, a thorough calculation of the Judd–Ofelt parameters and radiative properties has been carried out. The predicted spontaneous transition probability, emission cross section and gain coefficient of Ho3+:5I7→5I8 can reach to 74.11s−1, 4.53×10−21cm2, and 0.8cm−1, respectively. Besides, the energy transfer coefficients from Yb3+ to Ho3+ have also been calculated and discussed. The results suggest the prepared glass is a good candidate for efficient 2μm laser.

Fluorescence characteristics and energy transfer of ytterbium-sensitized erbium-doped fluorophosphate glass for amplifier applications

Yb3+/Er3+ codoped fluorophosphate glass has been investigated for developing broadband waveguide amplifier application. Spectroscopic properties and energy transfer microparameters of prepared glasses have been discussed. The spectral components of 1.55μm emission are analyzed and an equivalent four-level system is proposed to estimate the stark splitting for the 4I15/2 and 4I13/2 levels in Er3+ doped fluorophosphate glass. The results indicate that highly doped Yb3+ ions could transfer energy to Er ions efficiently in fluorophosphate glass and Er3+/Yb3+ doped fluorophosphate glass is preferable for broadband Er3+-doped waveguide amplifier application.