Doped Phosphate Glasses Research Articles

Optical and luminescence studies of Nd3+ doped phosphate glasses for pulsed laser applications

A series of glass with appropriate chemical compositions (60-x) P2O5 + 20 Bi2O3 + 10 SrF2 + 10 Na2 CO3 + x Nd2O3, (x = 0.1, 0.5, 1.0, 1.5, and 2.0% by mole) were prepared by using the melt quenching technique. The glass phase structure was confirmed by using X-ray diffraction technique. The structural analysis using FTIR technique it reveals characteristic bonding vibrations and different functional group in the glass matrix. The elements present in the fabricated glass sample was analyzed by using EADX spectrum. J-O intensity parameters Ω2, Ω4, and Ω6for the currently being researched PBNSNd10 glass have values of 9.80 × 10-20 cm2, 3.305 × 10-20 cm2, and 5.576 × 10-20 cm2 sequentially. The J-O parameters shows a trend of Ω2 > Ω6 > Ω4. The near infrared emission spectra recorded with 808 nm laser diode excitation for various concentrations of neodymium ions show the emission intensity is highest for the 4F3/2 → 4I11/2 transition at 1056 nm. The measured decay times 4F3/2 level decreased with increasing Nd2O3 ions because of concentration quenching effect. The obtained results in present study have been compared with previous results obtained for Nd2O3 doped glasses.

Effect of TeO2 on optical and 1.06 µm emission in Nd3+-doped phosphate glass for high-power lasers

In this work, we deal with glass composition, 29P2O5+(60−x)ZnO+10Na2O+xTeO2 (x=5−40mol.%) doped with 1 mol.% of Nd2O3. The samples are characterized by x ray diffraction, micro-Raman, optical absorption, and photoluminescence techniques. Refractive index (n) linearly increased with TeO2 content, as well as the optical basicity (Λ) due to the strengthening of the covalent bond between cation and oxide ions. Such information was corroborated by Raman spectra via an increase of non-bridging oxygens. The maximum phonon energy is approximately 1010cm−1, which is lower than reported for P2O5−ZnO−Na2O phosphate glass (1164cm−1). Detailed spectroscopic and luminescent properties based on TeO2 content are discussed. From luminescence spectra, laser parameters were estimated, viz., radiative transition probabilities, radiative lifetimes, branching ratios, and emission cross sections. The results show that the optimal laser emission parameters are obtained for TeO2 content equal to 20 mol.%, which evinces this glass composition as a promising host material for 1.06 µm high-power laser applications.

Optical spectroscopy assessment of the impact of γ-ray irradiation on Gd3+-doped phosphate glass

The effects of γ-ray irradiation (10, 100 kGy) on Gd3+-doped phosphate glass were evaluated. Glass irradiated at 100 kGy was characterized alongside the pristine by differential scanning calorimetry, Fourier transform-infrared spectroscopy and Raman scattering, wherein a lack of alteration in thermal and structural properties was supported. Yet, absorption bands developed around 500 nm with γ-ray dose indicating phosphorus oxygen hole center defects. Optical band gap and Urbach energies exhibited decreasing and increasing trends, respectively, reflecting the influence of trapped electrons and increased disorder/defects. By exciting γ-irradiated samples at 265 nm, blue radio-photoluminescence was observed where intensity increased with dose. Decay curves measured monitoring 415 nm emission showed first-order kinetics suggested to arise from phosphorus electron centers. Emission from Gd3+ was quenched with gamma-ray dose while the 6P7/2 emitting state lifetimes decreased. Correlations between Gd3+ emission intensities and lifetimes with optical band gaps suggest electron center defects perform as ‘energy sinks’.

Predicting and optimizing the physical and spectroscopic properties of phosphate laser glasses using a phase diagram approach

AbstractDespite the significant technological applications of laser glasses, the quantitative prediction and optimization of their properties, particularly the spectroscopic properties, remain challenging. Here we address this problem by regarding the nearest‐neighboring congruently melting compounds as the “component and structural motifs” based on the phase diagram approach. The composition–structure–property (CSP) relationships of Nd3+‐doped ternary phosphate glasses are investigated. Spectroscopic properties are quantitatively predicted with an error of less than 10% compared to the experimental results. In particular, the fluorescence lifetime (τm) can be accurately calculated using the phase diagram approach, which is difficult to be predicted previously. Furthermore, the CSP databases with over 1000 compositions are established for the optimization of commercial laser glasses. This study enriches the CSP database of traditional laser glass and provides guiding significance for future research.

Efficient laser operation with low loss Nd3+-doped phosphate glass fiber under direct pumping

For the first time, we have demonstrated efficient 1054 nm laser output with low loss Nd3+-doped phosphate glass fibers at room temperature using an 888 nm laser diode as the direct pumping source. Therein, the home-made Nd3+-doped phosphate glass fiber is the key for laser performance improvement. The transmission loss of the large-core single-cladding Nd3+-doped phosphate fibers prepared by the novel peeled-off isolated stacked extrusion method is as low as 1.1 dB/m at ∼1 μm. On this basis, a low-loss Fabry-Perot cavity is constructed by precisely controlling the relative distance between the fiber end facet and the cavity mirror with a microscope. The record-breaking optical-to-optical efficiency of Nd3+-doped phosphate glass fiber lasers, 50.2% is achieved with the maximum output power of 6.71 W. During laser operation, the output laser power does not roll over, even at high pump powers. The output laser power is limited only by the available pump power. This work will lay a solid foundation to the high-power fiber laser fabrication, and will find many applications in the future.

Excitability cultivation in high-energy UV region for Dy3+ in phosphate glass phosphors

Effective excitation region of Dy3+ has been expanded from low-energy ultraviolet (UVA) to high-energy ultraviolet (UVC) by the introduction of sensitizers into Dy3+ doped phosphate (NMBAP) glass phosphors. The cooperative effect of the sensitizers Ce3+ and Sb3+ generate remarkable enhancement on the fluorescence emission of Dy3+, attributing to the broadening of energy transmission channel to Dy3+. Diversified sensitization gain effects from tri-doped glass phosphors are discovered, providing a novel choice for the fluorescent optimization of Dy3+. Spectrum and image tracking confirm the Ce3+ and Sb3+ included Dy3+ doped NMBAP glass phosphors possess outstanding excitation response in whole UV region, which compensates the deficiencies in Dy3+ single-doped case. Intense fluorescence sensitization and delightful excitation extending in high-inclusive phosphate glass phosphors provide feasible routes for developing optoelectronic devices of light conversion, radiation detecting and laser illumination.

Down-shifting photoluminescent properties of Tb3+ doped phosphate glasses for intense green-emitting devices applications

Tb3+ doped BZLP glasses were prepared via a melt-quenching route and investigated thoroughly using spectroscopic techniques such as XRD, UV-VIS absorption and photoluminescence (PL) to explore their utility in visible photonic device applications. The information pertaining to glass transition temperature, melting temperature, and thermal stability were understood by using recording the differential scanning calorimetry (DSC) spectrum for an undoped BZLP glass. The total weight loss during the glass composition melting process was analyzed using Thermogravimetric curves. The UV spectral information recorded for the titled glasses reveals the optical bandgap falling in the range from 4.57 to 4.19 eV. The prepared Tb3+ doped BZLP glasses exhibit intense green emission along with relatively less intense blue, yellow, and red peaks under 373 nm excitation. In the resultant PL spectra, the emission intensity increases with the activator concentration of Tb3+ ions from 0.5 to 5.0 mol%. The estimated CIE chromaticity coordinates falling in the green region reveal the aptness of the titled glasses as a green constituent in visible photonic devices. The PL decay curves show the bi-exponential behavior with an average decay time of 2–3 ms. The temperature-dependent PL profile shows fewer changes in spectra and has a relatively high activation energy value, confirming the high thermal stability. Various results obtained for Tb3+ doped BZLP glasses finally reveal their usage as a green emitter needed to fabricate w-LEDs and other green-emitting photonic device applications.

High-order mode waveguide amplifier with high mode extinction ratio written in an Er3+-doped phosphate glass.

Inscription of fiber-compatible active waveguides in high-gain glass, followed by direct interconnection with few-mode fibers, is one of the most promising solutions for all-optical mode-division multiplexing. In this work, based on the femtosecond laser writing technique, we propose a general fabrication scheme for inscribing high-order mode waveguides in glass, by carefully tailoring the cross-section of the waveguides to match the mode intensity distribution via an improved multi-scan approach. Specifically, we design and fabricate two kinds of waveguides, namely, LP01-mode waveguide and LP11-mode waveguide in a highly Er3+-doped phosphate glass, enabling the insertion loss of the waveguides to be as low as 1.88 dB, and the mode extraction factor of the LP11-mode waveguide up to ∼24 dB. Importantly, we have successfully achieved optical amplification of the waveguides, with an on-off gain as high as 3.52 dB. This novel high-order mode waveguide amplifier has broad application prospects in monolithic on-chip integrated photonic light sources and optical interconnection with few-mode fiber and/or silicon-based waveguide.

Niobium incorporation into rare-earth doped aluminophosphate glasses: Structural characterization, optical properties, and luminescence

Luminescent Rare Earth (RE3+) doped phosphate glasses with molar composition (1-x)(60P2O5 – 15ZnO – 5Al2O3 – 10BaO – 10PbO)-xNb2O5 (x = 0, 10, 20 and 30 wt%) doped with 1.0, 1.2 and 0.3 wt% of Eu2O3, Yb2O3 and Er2O3, respectively, were prepared by conventional melt cooling. The glasses were characterized by optical reflectance, Raman scattering, and multinuclear (31P, 27Al, and 93Nb) solid-state NMR spectroscopy. Monotonic 31P chemical shift changes as a function of Nb2O5 content are consistent with the successive formation of Nb-O-P linkages. Aluminum is found in four-, five-, and six-coordination, with a successive decrease in average coordination number with increasing niobium content, while 93Nb NMR indicates three distinct niobium environments in these glasses. Incorporation of Nb2O5 has the expected effects on refractive index values, optical basicity, optical electronegativity, Urbach Energy, and the indirect bandgap, while RE3+ emission properties are only slightly modified. Under UV excitation, narrow emission bands are observed arising from 5D0→7FJ (J = 0, 1, 2, 3, and 4) transitions of Eu3+. At least two distinct Eu3+ lifetime values are observed, suggesting a spread of different ionic environments within the glass structure. Co-doping with Er3+/Yb3+ promotes emission in the infrared region, with a emission band maximum near 1535 nm and a width of 30.65 nm under excitation at 980 nm. Based on the results, these glasses may be potential candidates for energy conversion from infrared or UV region to the visible region and also infrared solid-state emitters.

Gamma-Ray Sensing Properties of Nd Doped Phosphate Glasses

Five selected Nd2O3 doped phosphate glass compositions are synthesized using melt quench technique. The physical properties such as density (ρ) and molar volume (Vm) are experimentally measured. The density increases whereas molar volume decreases with addition of Nd2O3 content. The radiation sensing properties for these rare earth (RE) element doped phosphate glass samples have been investigated. The photon attenuation and sensing parameters such as mass attenuation coefficient (μm), linear attenuation coefficient (μL), optimum thickness range (x opt), effective atomic number (Zeff), and mean free path (mfp) values are computed over wide gamma-ray energy range 1keV -100 GeV within framework of WinXCom software tool. The photon sensing properties of these rare earth doped phosphate glasses vary significantly on account of neodymium oxide content and photon energy. The mean free path (mfp) values of glass samples are found to decrease while the mass attenuation coefficient values rise as Nd2O3 concentration does.

UV to NIR Down-Shifting in Yb3+-Doped Phosphate Glass via Divalent Tin Centers

The conversion of ultraviolet (UV) to near-infrared (NIR) photons is demonstrated for the first time in Yb3+-containing glass via Sn2+. Glasses with barium phosphate matrix were prepared by melt-quenching adding 2 mol % Yb2O3 alongside SnO up to 10 mol %. The investigation encompassed X-ray diffraction (XRD), UV–vis-NIR absorption, 119Sn Mössbauer spectroscopy, and photoluminescence (PL) spectroscopy measurements with emission dynamics assessment. XRD data showed that the amorphous nature of the glasses is maintained within the range of dopant concentrations considered, while the optical absorption, 119Sn Mössbauer, and PL data supported the occurrence of divalent tin centers. The NIR PL data showed that exciting Sn2+ centers around 290 nm results in the NIR emission from Yb3+ near 1000 nm which becomes more intense with the increase in SnO. The Yb3+ decay curves revealed a rise time for the 2F5/2 emitting level followed by a single exponential decay. An energy transfer process proceeding via charge transfer states involving tin (donor) and ytterbium (acceptor) was proposed to account for the enhanced UV-excited NIR emission from Yb3+ ions.

The usability of the Judd-Ofelt theory for luminescent thermometry using Eu3+-doped phosphate glass

The Judd-Ofelt theory, which is the most thorough and insightful method to determine theoretically the luminescent properties of the trivalent rare earth dopants, is here tested on Eu3+-doped glasses in the P2O5 – SrO – CaO – Na2O system to assess their usefulness as luminescent thermometers. It is demonstrated that the thermometric sensitivity (change of the emission lines ratio in response to change in temperature) can be estimated using the Judd-Ofelt theory and aligns well with the experimentally obtained values. It is shown here that the addition of B2O3 or SiO2 in a phosphate network increases the absolute sensitivity due to an increase in the phosphate network connectivity while having no significant impact on the site of Eu3+ ions. The applicability of the Judd-Ofelt theory for predicting the thermometric parameters of a glass luminescent material, without the time-consuming measurement of the glasses spectroscopic properties as a function of temperature, is clearly demonstrated and allows for further development of novel efficient luminescent thermal sensors with high sensitivity.

Impact of Al2O3, TiO2 and ZnO addition on the crystallization of Yb3+ doped phosphate glass-ceramic

New Yb3+-doped phosphate glasses with a composition of (98.75-x) (90 NaPO3 – 10 Na2O) – x (Al2O3, TiO2, or ZnO) – 1.25 Yb2O3 (in mol-%), with x from 0 to 3, were prepared via conventional melting and quenching process. The thermal and physical properties were studied by differential thermal analysis (DTA) and density measurement, respectively. The glass structure was investigated using visible/infrared spectroscopy and the crystallization properties of the glasses using XRD. Changes in the glass composition were found to have an impact on the glass structure and more importantly on the crystallization process; the addition of Al2O3, TiO2 and ZnO promotes the precipitation of the Na5P3O10 crystalline phase at the expense of NaYb(P2O7) and NaPO3 phases and more importantly, promotes surface crystallization at the expense of bulk crystallization.

Investigation of europium-doped aluminium phosphate glass for red light generation

Europium doped phosphate glasses (KPEu) with various concentrations of Eu 2 O 3 were prepared by a melt-quenching method for red light application. The prepared samples were characterized using physical, absorption, photoluminescence, X-ray induced luminescence (XEL) and J-O analysis techniques. Density, molar volume and refractive index of the investigated glasses increased with increasing concentration of Eu 2 O 3 . Eight absorption peaks were observed, with six peaks in the visible region (350–550) nm and two in the infrared region (2000–2200). Four emission peaks were observed in the visible region when the glass was excited at 394 nm. Judd-Ofelt (JO) intensity parameters (Ω λ λ = 2, 4, 6) were determined using the JO-theory for the prepared glass samples. The radiative properties of the glasses were determined using JO-parameter, refractive index and emission spectra. The trend of JO parameters for the present KPEu 6 glass sample were Ω 2 > Ω 4 > Ω 6 . These glasses also showed higher branching ratios and stimulated emission cross section ( σ e ) values, making these suitable for red laser applications. XEL showed the same peaks and trend as emission spectra but its peaks were shifted and had high intensity. The luminescence colours of these glass samples entirely fall in the reddish orange region (x = 0.653–0.654, y = 0.346–0.347) as confirmed by CIE 1931 diagram. The CCT values of the prepared glass samples were in the range of 2394–2431 K.

Investigation on luminescence properties and energy transfer of Gd3+ and Sm3+-doped phosphate glass for solid-state lighting

The physical and optical properties of glasses for solid-state lighting applications are being investigated. The melt quenching procedure at 1200 °C was used to create the Gd3+ and Sm3+ ions using doped phosphate-based glasses. Gd2O3 and Sm2O3 concentrations increased density, according to the findings. For the alteration in the glass, the intensity of molar volume rose, indicating the establishment of a non-bridging oxygen (NBO) network. The absorption spectra migrated from 6H5/2, the ground state, to different states with wavelengths ranging from 300 to 1700 nm. When the energy transfer from the IH model is at its greatest at 11 mol% Gd3+ concentration, photoluminescence spectra exhibit four emission peaks ranging from 4G9/2 to 6H5/2, 6H7/2, 6H9/2, and 6H11/2, respectively. The maximum photoluminescence spectra intensity was 1 mol% of Sm2O3, which was compared to bismuth germanium oxide (Bi4Ge3O12; BGO) crystal at 10.33% by x-ray excitation. The color of orange emission is determined by the CIE 1931. The Judd-Ofelt (JO) parameter (Ωλ (λ = 2, 4, 6)) have been used by evaluated Judd-Ofelt theory and trend were Ω4 > Ω6 > Ω2. As a result, doped phosphate base glasses with Gd3+ and Sm3+ ions have property requirements, and cost-cutting production is the best option for solid-state lighting applications.

Spectroscopic characterizations of Dy3+ ions doped phosphate glasses for epoxy-free white LED applications

The present work illustrates a detailed spectroscopic analysis carried out on dysprosium ions doped Zinc Alumino Sodium Phosphate (ZnAlNaP) glasses with chemical composition of (10-x)ZnO–20Al2O3–10Na2O–60P2O5-xDy2O3 (x = 0.1–2.0 mol%). The XRD spectra verified for an un-doped and Dy3+ ions doped ZnAlNaP glasses demonstrate an enormous hump confirming its amorphous behavior. The FT-IR and Raman spectrum recorded for an un-doped ZnAlNaP and ZnAlNaPDy1.0 glass elucidates various functional groups and vibrational modes involved, respectively. The DSC & TGA studies conducted on an un-doped ZnAlNaP glass revealed its thermal stability and overall weight loss. The absorption spectra were used to calculate the optical bandgap for the as-synthesized glasses and were found to be in the range of 2.9 eV–4.7 eV. Photoluminescence (PL) excitation, emission and decay spectral analysis were done to investigate the suitability of the as-synthesized glasses for epoxy-free solid-state lighting (SSL) devices. The PL emission recorded under 350 nm excitation show two significant bands in blue and yellow regions. Temperature-dependent PL studies conducted on ZnAlNaPDy1.0 glass revealed activation energy of 0.212 eV with a 25.6% loss in PL intensity. The CIE color chromaticity coordinates and correlated color temperature (CCT) were calculated from the PL spectral characteristics. All the spectroscopic investigations conducted on the as-synthesized ZnAlNaPDy glasses finally reveal their superior nature for fabricating epoxy-free white-light emitting diodes (w-LEDs).

Synthesis and characterization of rare-earth doped aluminium phosphate glasses

Sodium aluminium phosphate (NAP) glass is a potential candidate for the immobilization of minor actinides (MA). The composition of the NAP glass 38Na2O–30Al2O3–32P2O5 (mol %) was found to be the optimal choice, through experimental trials and specimens of this glass containing 1, 5, 10 and 15 wt% of the rare-earths (Ce, Pr, Nd and Gd-as surrogates for MA) were prepared by the melt quench technique. All these samples were X-ray amorphous, and were found to contain (PO4)−2 Q1 and (PO4)−1 Q2 units. Both Al2O3 and rare-earths were found to modify the structure of the phosphate glass significantly. Al2O3 plausibly acts as a network former at higher concentrations. The melting point, glass transition temperature, viscosity, Angell thermal stability and glass forming ability of these glasses increase with the concentration of the dopants, while their fragility decreased. Absolute values of the heat capacity of these glasses (Cp) as well as the attendant change in the heat capacity during the glass transition ΔCp showed an increase up to 5 wt % doping and a decrease subsequently when the concentration of the dopants were increased up to 15 wt%. Glasses containing 10 and 15 wt% dopants show sharper crystallization peaks while the crystallization is less pronounced in the rest of the glass samples. The rare-earth cations improve the strength of the glass when doped up to 5 wt%, beyond which the rigidity of the structure begins to fall. The networking due to complexation diminishes and leads to weaker chains resulting in the glasses with higher concentration of the rare-earths modifiers. These first results on the dependence of the structure and thermal properties of the NAP glass 38Na2O–30Al2O3–32P2O5 (mol%) doped with rare-earth reported here show that this glass could serve as a suitable matrix for immobilizing rare earths and minor actinides.

Ultrafast fiber laser at 0.9 µm with a gigahertz fundamental repetition rate by a high gain Nd3+-doped phosphate glass fiber.

Fiber lasers, owing to the advantages of excellent beam quality and unique robustness, play a crucial role in lots of fields in modern society. Developing optical glass fibers with superior performance is of fundamental importance for wide applications of fiber lasers. Here, a new Nd3+-doped phosphate single-mode fiber that enables a high gain at 0.9 µm is designed and fabricated. Compared to previous Nd3+-doped silica fibers, the developed phosphate fiber exhibits a significant gain promotion, up to 2.7 dB cm-1 at 915 nm. Configuring in a continuous-wave fiber laser, this phosphate fiber can provide a slope efficiency of 11.2% in a length of only 4.5 cm, about 6 times higher than that of Nd3+-doped silica fiber. To showcase its uniqueness, an ultrafast fiber laser with ultrashort cavity is constructed, such that an ultrashort pulse train with a fundamental repetition rate of up to 1.2 GHz is successfully generated. To the best of our knowledge, this is the highest fundamental repetition rate for mode-locked fiber lasers at this wavelength range - two orders of magnitude higher than that of prior works. These results indicate that this Nd3+-doped phosphate fiber is an effective gain medium for fiber amplifiers and lasers at 0.9 µm, and it is promising for two-photon biophotonics that requires long-term operation with low phototoxicity.

Tuneable luminescence of Pr3+-doped sodium aluminium gadolinium phosphate glasses for photonics applications

Pr3+ doped sodium aluminium gadolinium phosphate (Pr:NaAlGdP) glasses were prepared to characterize on the structure, physical and especially spectroscopic properties. From XRD and FTIR results, synthesized glasses had the amorphous nature with phosphate complexes as the main structure units. The density, molar volume and refractive index of glass increased with increment of Pr2O3 concentration. The absorption spectra demonstrated the strong absorbance of Pr3+ dopant in visible light and near infrared region. The emission spectra recorded under 444, 468 and 481 nm excitation exhibited overlapping of Pr3+ emission from two emitting levels, 1D2 and 3P0. The 1D2→3H4 transition was of the highest intensity with emission maxima at 600 nm. The distinct excitation wavelengths caused the different emission patterns, resulting to the tuneable color of emission as pink, orange, and reddish orange. The optimum concentration of Pr2O3 in NaAlGdP glass is 0.1 mol% with the highest photoluminescence intensity and the 2nd longest decay time in hundred microsecond order. The non-single exponential decay profile and the reduction of decay time with added Pr2O3 content indicated the resonant energy transfer between Pr3+ ions. The high values of stimulated emission cross-section, branching ratio and quantum efficiency from Judd-Ofelt analysis confirmed the potential lasing action and light emitting with 600 nm from this glass. The radioluminescence study also represented the interesting ability of glass for X-ray detection. The Pr:NaAlGdP glass is a promising new photonics material for the tuneable light source, LED, display / screen, waveguide and laser medium.

Investigation of spectroscopic properties of Sm3+ doped phosphate glasses for reddish orange light applications

Samples of phosphate glasses with composition of (40-x) P2O5-40Na2O-20ZnO-xSm2O3, with Sm3+ ion concentration varying from 0.1 to 2.5%, were synthesized using melt quenching technique and characterized by X-Rays Diffraction, UV–Vis and luminescence spectroscopies. Using Judd-Ofelt analysis, the parameters Ω2, Ω4 and Ω6 of Sm3+ (4f7) were determined. Three transitions of Sm3+: 4G5/2→ 6H5/2, 6H7/2, 6H9/2 were observed from the luminescence spectra. The radiative (τr) and the measured (τmea) lifetimes for 4G5/2 level, were discussed and compared with other works. The quantum efficiency (η) is found to be higher for × = 0.5 mol % of Sm2O3. The CIE chromaticity coordinates were calculated, and it was found that PSm glasses can be suitable for the development of visible lasers in the orange red spectral region.