Quantitative prediction of the glass-forming region and luminescence properties in Tm3+-doped germanate laser glasses

Germanate laser glasses have received much attention as a promising host materials for mid-infrared fiber lasers in recent years because of the outstanding infrared transparency, low phonon energy, and high rare earth solubility of such glasses. However, the development of high-performance germanate laser glasses is usually based on intuition and a trial-and-error method, which can involve long experimental periods and high costs, and thus, this approach is highly inefficient. Recently, with proposals for materials genome engineering, the concept of the “glass genome” has grown of interest to us. Herein, the structures of Tm³⁺-doped germanate laser glasses (BaO–GeO₂ and BaO–La₂O₃–GeO₂) were investigated by Fourier transform infrared spectra (FTIR) and Raman spectra analyses, which revealed that the resulting glass contains similar structural groups to the neighboring congruently melted glassy compounds (NCMGCs) in the composition diagram. What is more, the structure and properties of the resulting laser glasses largely depend on NCMGCs. Then, the glass-forming region, physical properties, and luminescence properties were calculated via the use of NCMGCs in Tm³⁺-doped BaO–GeO₂ binary and BaO–La₂O₃–GeO₂ ternary laser glass systems. The calculated results were in good agreement with the experimental results, thus demonstrating that our approach is practical for predicting the glass-forming region, physical properties, and luminescence properties in Tm³⁺-doped BaO–GeO₂ binary and BaO–La₂O₃–GeO₂ ternary laser glass systems. This work may provide an effective method to develop Tm³⁺-doped germanate laser glasses rapidly and at low cost.     

Improved broadband near-infrared luminescence in Nd3+/Tm3+ co-doping tellurite glass with Ag NPs

The near-infrared (NIR) luminescence in S+E+O bands of tellurite glasses doped with Nd³⁺/Tm³⁺ and Ag nanoparticles (NPs) was investigated. The tellurite glasses were prepared by melt-quenching and heat-treated techniques. Under the excitation of 808 nm laser, Nd³⁺/Tm³⁺ doped tellurite glasses produced three NIR luminescence bands of 1.33, 1.47 and 1.85 μm, originating from Nd³⁺:⁴F_3/2→⁴I_13/2, Tm³⁺:³H₄→³F₄ and Tm³⁺:³F₄→³H₆ transitions respectively. Interestingly, a broadband luminescence spectrum ranging from 1280 to 1550 nm with the FWHM (full width at half maximum) about 201 nm was obtained due to the overlapping of the first two NIR bands. Further, the peak intensity of this broadband luminescence was increased by 75% after the introduction of Ag NPs with diameter in 10–20 nm. The analysis of fluorescence decay shows that compared with the enhanced local electric field, the energy transfer from Ag species to Nd³⁺ and Tm³⁺ ions plays a major role in luminescence enhancement. The findings in this work indicate that tellurite glass co-doped with Nd³⁺/Tm³⁺ and Ag NPs is a potential gain material applied in the S+E+O-band photonic devices.     

Mechanism for broadening and enhancing Nd3+ emission in zinc aluminophosphate laser glass by addition of Bi2O3

Nd³⁺-doped phosphate laser glasses have been attracting much attention and widespread investigation due to their high solubility of rare earth (RE) ions, excellent spectroscopic properties, and large damage threshold. However, the narrow NIR emission bandwidth (less than 30 nm) of these Nd³⁺-doped phosphate glasses limits their further application toward ultrahigh power field and efficient fiber laser in new region. Here, we demonstrate the broadening and enhancing of Nd³⁺ NIR emission in laser glass of zinc aluminophosphate through tuning the glass structure and covalency of Nd-O bond without limiting the radiative properties of Nd³⁺. The maximum bandwidth of 1.05 μm emission is broadened to 50 nm, which is comparable to that of Nd³⁺-doped aluminate laser glasses. Simultaneously, the lifetime of ⁴F_3/2 level is elongated nearly by two times. Structural and optical properties of prepared glasses were discussed systematically to reveal the mechanism. Detailed analysis on optical spectra and glass structure indicates that the bandwidth is affected by not only the covalency of Nd-O but also the compactness of glass structure. Our results could enrich our understanding about the relationship between local glass structure and luminescence behaviors of active centers, and may be helpful in designing new RE-doped laser glass systems.     

Photodarkening mechanisms of Pr3+ singly doped and Pr3+/Ce3+ co-doped silicate glasses and fibers

In this work, we revealed the possible mechanisms of the photodarkening in Pr³⁺ ions singly doped and Pr³⁺/Ce³⁺ co-doped silicate glasses and fibers induced by X-ray and 488-nm laser radiations and studied the role of Ce³⁺ in increasing radiation resistance in Pr³⁺-doped silicate glasses and fibers. The absorption, emission, electron paramagnetic resonance (EPR), radiation induced attenuation spectra, and X-ray photoelectron spectroscopy (XPS) of Pr³⁺ singly doped and Pr³⁺/Ce³⁺ co-doped silicate glasses before and after X-ray radiation were measured and analyzed. The fluorescence intensity and photoinduced attenuation of Pr³⁺ singly doped and Pr³⁺/Ce³⁺ co-doped silicate fibers at visible wavelengths pumped by 488-nm laser were measured and analyzed. The influence of Ce³⁺ ions co-doping on the spectroscopic properties of Pr³⁺ ions as well as the radiation-induced defects in silicate glasses was studied. Results demonstrate that both X-ray and 488-nm laser radiations will induce photodamage in Pr³⁺ ions-doped silicate glasses and fibers. Co-doping Ce³⁺ (by up to 1 mol%) is efficient to suppress the darkening induced by both X-ray and 488-nm laser radiations without influence on the luminescence behavior of Pr³⁺ ions in silicate glasses and fibers. Our studies demonstrate the promising potential of Pr³⁺/Ce³⁺ co-doped silicate glasses for visible lasing applications.     

Blue Upconversion Emission in Germanate Glass Co-Doped with Yb3+/Tm3+ Ions

In the paper, the upconversion luminescence of 70GeO₂–30[Ga₂O₃–BaO–Na₂O] glass system co-doped with Yb³⁺/Tm³⁺ ions was investigated. Strong blue emission at 478 nm corresponding to the transition ¹G₄ → ³H₆ in thulium ions was measured under the excitation of 976-nm diode laser. The dependence of the upconversion emission upon the thulium ion concentration was studied to determine the optimal conditions of energy transfer between energy levels of active dopants. The most effective energy transfer Yb³⁺ → Tm³⁺ was obtained in glass co-doped with molar ratio of dopant 0.7 Yb₂O₃/0.07 Tm₂O₃. The increase in thulium concentration more than 0.07 mol% results in the reverse energy transfer from Tm³⁺ → Yb³⁺, which leads to rapid quenching of the luminescence line at the wavelength 478 nm. In germanate glass co-doped with 0.7Yb₂O₃/0.07Tm₂O₃, the longest lifetime of ¹G₄ level equal 278 μs was achieved. The presented results indicate that elaborated germanate glass co-doped with Yb³⁺/Tm³⁺ ions is a promising material that can be used to produce fiber lasers and superluminescent fiber sources generating radiation in the visible spectrum.     

Doped tellurite glasses: Extending near-infrared emission for near-2.0-μm amplifiers

Tm³⁺-singly-doped and Tm³⁺-/Ho³⁺-codoped TeO₂-Bi₂O₃-ZnO-Li₂O-Nb₂O₅ (TBZLN) tellurite glasses were successfully prepared by the melt-quenching technique. Emission characteristics and energy transfer mechanisms were studied upon 785-nm laser diode excitation. A significant enhancement of emission intensity at 1.81 μm with increasing concentration of Tm³⁺ ions has been observed while increase in the emission intensity at 2.0 μm with increasing concentration of Ho³⁺ has been observed up to the equal concentration of Tm³⁺ (0.5 mol%) in TBZLN glasses. The stimulated emission cross section of Tm³⁺: ³F₄→³H₆ (5.20×10⁻²¹ cm²) and Ho³⁺: ⁵I₇→⁵I₈ (4.00×10⁻²¹ cm²) in 1.0 mol% Tm³⁺-doped and 0.5 mol% Tm³⁺/1.0 mol% Ho³⁺-codoped TBZLN glasses are higher compared with the reported and are found to be excellent candidates for solid-state lasers operating at ~1.8 and 2.0 μm, respectively. The extension of near-infrared (NIR) emission of Tm³⁺ with Ho³⁺ ions provides the possibility of using these materials for broadband NIR amplifiers.     

Realization of pure red emission from energy transfer in the Er3+–Tm3+ system under 1550 nm excitation

NaY(WO₄)₂ is one of the excellent host materials for high-efficient upconversion luminescence, but it is still challenging to obtain red emission via lanthanide doping. In this work, pure red emission was achieved in the heavily-Er³⁺-doped NaY(WO₄)₂ by using a 1550 nm laser diode and introducing mediator Tm³⁺ ions in the lattice. On basis of the analysis of steady-state and transient-state luminescence properties related to dopant concentration and excitation wavelength, all possible red emission mechanisms were discussed. Finally, it has been demonstrated that the high-purity red emission was due to the several energy transfer processes between Er³⁺ and Tm³⁺. Our results provide a convenient pathway to investigate the upconversion luminescence mechanisms.     

Ce3+ induced broadband enhancement around 2 μm in Tm3+/Ho3+ co-doped tellurite glass

Tellurite glasses doped with Tm³⁺, Ho³⁺ and Ce³⁺ ions were prepared via melt-quenching to realise broadband and fluorescence enhancement in near-infrared (NIR) band. Under the pumping of a commercial 808 nm laser diode (LD), the emission bands at 2.0 μm, 1.85 μm, 1.47 μm, and 705 nm were observed in the Tm³⁺/Ho³⁺ co-doping glass samples, which originated from the transitions of Ho³⁺:⁵I₇→⁵I₈ and Tm³⁺:³F₄→³H₆, ³H₄→³F₄, ³F_2,3 → ³H₆, respectively. The existence of 2.0 μm band fluorescence is due to the energy transfer from the Tm³⁺:³F₄ level to the Ho³⁺:⁵I₇ level. This band overlaps with the 1.85 μm band which forms a broadband fluorescence spectrum in the range of 1600–2200 nm. In glass samples co-doped with Tm³⁺/Ho³⁺ with 0.085 mol% Ho₂O₃ and 1 mol% Tm₂O₃, the full width at half maximum (FWHM) of this broadband spectrum (1600–2200 nm) was as high as ∼370 nm. After introducing 0.6 mol% CeO₂, the emission intensity of broadband fluorescence increased by ∼50%, which was caused by the cross-relaxations between Ce³⁺ and Tm³⁺ ions. The lifetime of fluorescence decay was determined to prove the interactions among the doped rare-earth ions, the radiative parameters such as transition probability, branching ratio and radiative lifetime were calculated from the absorption spectra based on the Judd-Ofelt theory to better understand the observed luminescence phenomena. In addition, X-ray diffraction (XRD) confirmed the amorphous state structure of the synthesised glass samples, while Raman spectrum revealed the different vibrational structural units forming the glass network.     

Effective sensitization of Eu3+ ions on Eu3+/Nd3+ co-doped multicomponent borosilicate glasses for visible and NIR luminescence applications

Eu³⁺/Nd³⁺ co-doped multicomponent borosilicate glasses (ND1E: 10BaO +10ZnF₂+10K₂O +20SiO₂+(49-x) B₂O₃+1Nd₂O₃+xEu₂O₃) were prepared by conventional melting and rapid quench technique to evaluate the effect of Eu³⁺ ions in the Nd³⁺ doped glasses. Thermal stability, structural and spectroscopic characteristics of the ND1E glasses were investigated by using DSC, XRD, FTIR, Optical absorption, excitation and emission measurements. The Judd – Ofelt (JO) analysis is implemented to the absorption spectrum of the prepared glassy matrix in order to identify their potential applicability in lasing devices. Enhancement of ⁷F₀ → ⁵L₆ band (394 nm) with the increasing concentration of Eu³⁺ ion in the Nd³⁺ excitation spectra (λ_emi = 1060 nm) reveals the possibility of obtaining the characteristic fluorescence spectra of Nd³⁺ ion with the typical excitation wavelengths (Nd³⁺ = 584 nm and Eu³⁺ = 394 nm) of both rare earth ions and it is further verified from the emission spectrum. This interesting luminescence effect of showing excellent visible and NIR emission under 394 nm excitation mainly attributes the energy transfer mechanism between the RE³⁺ ions and the reason underlying this effect is discussed in detail with the help of partial energy level diagram. Energy transfer efficiency between the Eu³⁺ and Nd³⁺ ions were evaluated by using the radiative lifetimes of the prepared glasses. Also, a comparison of radiative properties and lasing characteristics of Eu³⁺/Nd³⁺ co-doped glasses with other Nd³⁺ glasses are reported. The emission intensities were characterized using CIE chromaticity diagram and the observed CIE coordinates shows a shift towards reddish – orange region with the increase in Eu³⁺ concentration. The quantum efficiency of the prepared glasses was determined experimentally. The obtained results suggest that the ND1E glassy system can be considered as a potential candidate for visible and NIR luminescence applications.     

Multifunctional α-NaYbF4:Tm3+ nanocrystals with intense ultraviolet self-sensitized upconversion luminescence and highly efficient optical heating

Lanthanide-doped upconversion photoluminescent nanoparticles with unique anti-Stokes spectroscopic properties excel in many fields of application. Ytterbium-based self-sensitized fluorides with rich Yb³⁺ possess higher absorption efficiency of incident near infrared laser, and are more favorable for photoluminescence or optical heating applications. In this work, α-NaYbF₄:Tm³⁺ crystalline nanoparticles are synthesized, which exhibit intense ultraviolet self-sensitized upconversion photoluminescence and highly efficient optical heating capability under 980 nm laser excitation. NaYbF₄:Tm³⁺ nanocrystals emit multi-band luminescence with emission peaks located in the ultraviolet, blue and red spectral regions. The energy transfer mechanism and electronic transition pathways for the Upconversion luminescence are investigated based on the energy level scheme, and are further confirmed by luminescent dynamic analysis. Due to cross-relaxations between Tm³⁺ and energy back transfer from Tm³⁺ to Yb³⁺ processes, the NaYbF₄: 1 mol% Tm³⁺ nanoparticles possess the highest luminescence intensity. The luminescent dynamic characteristics, such as decay time and rise time, vary with Tm³⁺ doping concentrations. Highly efficient optical heating effect is observed in the NaYbF₄:Tm³⁺ nanoparticles with slope efficiency of photothermal conversion for 10 s laser irradiation is as high as 100.48 °C/W.     

Investigation of Pr3+ Near-Infrared Emission in Plasmonic and Dichroic Copper Nanocomposite Glasses

Melt-quenched Pr³⁺-doped phosphate glass containing Cu⁺ and Sn²⁺ as redox couple to induce Cu nanoparticle (NP) precipitation was subjected to heat treatment to develop nanocomposite glasses with plasmonic and dichroic character. The purpose was to examine the impact of Cu NPs producing dichroism on the near-infrared (NIR) emission from Pr³⁺. The parent and isothermally heat-treated glasses (520?°C: 20, 40, 60?min) were characterized by differential scanning calorimetry, Fourier transform-infrared spectroscopy, optical extinction, and photoluminescence spectroscopy with decay dynamics. From the samples, the heat-treated for 40 and 60?min showed broad plasmonic bands alongside dichroism wherein the glasses scatter red light but transmit blue. The Pr³⁺ NIR emission encompassing ¹D₂ → ³F₄, ³F₃,¹G₄ transitions was evaluated under 445 and 590?nm excitation. An increased emission was not exhibited, whereas a quenching effect became evident for samples heat-treated for 40 and 60?min. Different interactions involving Pr³⁺ ions and Cu NPs are discussed.

     

Tunable ultra-wideband NIR emission and irradiation resistance in novel Er3+/Tm3+/Pr3+ tri-doped La2O3- Ga2O3-Ta2O5 glasses synthesized using aerodynamic levitation method

Glasses with ultra-wideband near-infrared emission and superior irradiation resistance are important for the potential applications in optical communications under harsh environments. Here, transparent 35La₂O₃-(65-x)Ga₂O₃-xTa₂O₅ (LGT) and Er³⁺/Tm³⁺/Pr³⁺ tri-doped LGT glasses are fabricated using the levitation method. LGT glasses exhibit a wide glass-formation region, low largest vibration energy, high refractive indices, and excellent mechanical properties. Additionally, Er³⁺/Tm³⁺/Pr³⁺ tri-doped LGT samples with varying Pr³⁺ contents are characterized by possessing good thermal stability (T_g>849°C), wide transparent optical window, strong radiation resistance, excellent compatibility between low wavelength dispersion (v_d>31.2), and large refractive index (n_d>2.048). By optimizing the doping content of Er³⁺, Tm³⁺, and Pr³⁺ in an appropriate ratio, the ultra-wideband near-infrared luminescence ranging from 1250 to 1640 nm (FWHM = 251 nm) has been acquired under 808 nm pumping. Furthermore, decay curves are measured to reveal the fluorescence dynamics, and then the related emission mechanism is elaborated systematically. Meanwhile, the effects of gamma irradiation doses on microstructure, transmittance spectra, and fluorescence characteristics are studied. This work may offer a valuable reference for doping optimization and new design strategy of multifunctional materials.     

Site occupancy and enhanced luminescence of broadband NIR gallogermanate phosphors by energy transfer

Super broadband near-infrared (NIR) La₃Ga₅GeO₁₄(LGGO): Cr³⁺ phosphor is in urgent needs for food testing. Unfortunately, it suffers from poor luminescence intensity in applications. Herein, the enhanced NIR luminescence performance can be realized in LGGO: Pr³⁺, Cr³⁺. The preferential crystallographic site of Cr³⁺ is validated on the basis of EPR spectrum, Rietveld refinement, and the first-principles DFT calculations. It is of great importance that the as-prepared phosphors can be excited by blue light (460 nm), which is beneficial to the application of blue-pumped LEDs. The critical distance of Pr³⁺ in LGGO host has been calculated by concentration-quenching method. For co-doped sample, it is observed that Cr³⁺ luminescence intensity enhancement by a factor of 3 can be achieved by doping Pr³⁺ owing to the energy transfer from Pr³⁺ to Cr³⁺. In addition, the introduction of Pr³⁺ can also improve the Cr³⁺ luminescence intensity at elevated temperature. Furthermore, using the optimized phosphor, a blue-based NIR phosphor-converted LEDs (NIR pc- LEDs) is fabricated, the forward voltage and the intensity of LED hardly change after thermal aging for 500 hours under high temperature/ high humidity condition, indicating its great reliability for NIR pc-LEDs. Therefore, LGGO:Pr³⁺, Cr³⁺ has great potential to serve as an attractive candidate in the application of blue light-excited NIR pc-LEDs in view of its capability for blue to enhanced broadband NIR conversion.     

Spectroscopic properties of Yb2+ in aluminosilicate glass

In contrast to Yb³⁺ which is a well-investigated optically active ion, the spectroscopic properties of its divalent counterpart Yb²⁺ in glasses are hardly investigated, although Yb²⁺ might have a notable influence on the luminescence properties of Yb³⁺-doped glasses even at low Yb²⁺ concentrations because of its strong f-d transitions. In this paper, we report on the preparation and spectroscopic properties of Yb²⁺-doped aluminosilicate glasses that were produced using the normal melt-quench technique. The glass composition is 20CaO·20Al₂O₃·60SiO₂ (mol%). To achieve a sufficient amount of Yb²⁺ in the samples, different methods were applied to influence the red-ox equilibrium during glass melting: firstly, under argon atmosphere and additional argon bubbling, and secondly by the addition of metallic aluminum powder to the batch. The strongly reduced samples show a greenish to brownish yellow coloring which could be attributed to the strong absorption of Yb²⁺ ions in the UV to blue spectral range. The absolute Yb²⁺ concentration in the glass and the molar extinction coefficient of Yb²⁺ was obtained by spectroscopic measurements. If irradiated with UV light, the Yb²⁺-doped samples show a broad fluorescence emission in the wavelength range from 450 to 700 nm with a peak at around 515 nm.     

Effect of glass composition on the physical properties and luminescence of Pr3+ ion-doped chalcogenide glasses

In this work, Pr³⁺ ion-doped Ge₂₀Ga_15−xSb_xSe₆₅ (x = 0, 5, 10, in mol%), Ge₂₀Sb_15−yIn_ySe₆₅ (y = 5, 10, in mol%), Ge₂₀Ga_15−zIn_zSe₆₅ (z = 0, 5, 10, in mol%), and Ge₂₀Ga₅Sb₁₀Se₆₀I₅ glasses were prepared. The structural units, thermal properties, and optical properties of these glasses were analyzed. In addition, a comprehensive comparison study of the effects of metal ions (Sb, Ga, and In), S/Se ratio, and I content on the mid-infrared (MIR) luminescence of Pr³⁺ ions was conducted. Under a 1.55-μm laser pump, 0.2 mol% of Pr³⁺ ion-doped chalcogenide glasses performed strong photoluminescence in the wavelength range of 3.5-5.5 μm. Results indicated that the Sb-containing glass performed the strongest emission intensity among the studied glasses. Moreover, halogen element I can reduce the phonon energy of the matrix, which is beneficial to the luminescence of Pr³⁺ ions and provide significant possibilities for developing MIR lasers and amplifiers.     

Effect of BaF2 Content on Luminescence of Rare‐Earth Ions in Borate and Germanate Glasses

Rare‐earth‐doped oxyfluoride germanate and borate glasses were synthesized and next studied using spectroscopic methods. Influence of fluoride modifier on luminescence properties of rare earths in different glass hosts was examined. The excitation and emission spectra of Pr³⁺ and Er³⁺ ions in the studied glasses were registered. The emission spectra of Pr³⁺ ions in germanate and borate glasses are quite different and depend strongly on the glass host. In samples doped with Er³⁺ ions emission bands located around 1530 nm corresponding to the main ⁴I_13/2→⁴I_15/2 laser transition were registered, independently of the glass host. Quite long‐lived near‐infrared luminescence of Er³⁺ ions was observed for germanate glasses with low BaF₂ content, while in borate glass systems influence of barium fluoride on luminescence lifetimes is not so evident. The Judd–Ofelt calculations were used in order to determine quantum efficiencies of excited states of rare‐earth ions in germanate and borate glasses.     

Effect of introduction of TiO2 and GeO2 oxides on thermal stability and 2 μm luminescence properties of tellurite glasses

In this paper, Tm³⁺ doped pure tellurite glass, TiO₂ modified tellurite glass and TiO₂/GeO₂ co-modified tellurite glasses were prepared. The effects of the introduction of TiO₂ and GeO₂ oxides on the thermal, structural, optical properties of tellurite glasses were compared and analyzed intensively. Besides, the Judd-Ofelt intensity parameters and absorption and emission cross sections were calculated. DTA curves indicated the thermal stability of pure tellurite glass enhance obviously by GeO₂ modification. The introduction of TiO₂ and GeO₂ oxides in tellurite glasses arise a series of variation on the absorbance, luminescence peak position and fluorescence intensity which have been explained and analyzed in detail. Based on the analysis, the addition of TiO₂ in tellurite glass contributes to the improvement of 2 μm fluorescence performance, and the introduction of GeO₂ has great advantages in enhancing the thermal stability of glass.     

Gd3+ doping induced microstructural evolution and enhanced visible luminescence of Pr3+ activated calcium fluoride transparent ceramics

Transparent Pr³⁺ doped Ca_1-xGd_xF_2+x (x = 0, 0.01, 0.03, 0.06, 0.10, 0.15) polycrystalline ceramics with fine-grained microstructures were prepared by the hot-pressing method. The dependence of microstructure, optical transmittance, luminescence performances and mechanical properties on the Gd³⁺ concentrations for Pr³⁺:Ca_1-xGd_xF_2+x transparent ceramics were investigated. The Gd³⁺ ions show positive effects on the microhardness of Pr³⁺:Ca_1-xGd_xF_2+x transparent ceramics as a result of the decrease in the grain sizes. Excited by the Xenon lamp of 444 nm, typical visible emissions located at 484 nm, 598 nm and 642 nm were observed. Furthermore, the incorporation of Gd³⁺ ions can greatly enhance the photoluminescence performance owing to the improvement in the concentration quenching effect. The quenching concentration of Pr³⁺ ions in CaF₂ transparent ceramics increased to 1 at.% as a result of the positive effect of Gd³⁺ codoping. The energy transfer mechanism of Pr³⁺ in the Pr³⁺:Ca_1-xGd_xF_2+x transparent ceramics has been investigated and discussed.     

Detailed optical analysis of Dy3+ and Pr3+ co-doped alumino-borate glasses for visible lighting applications

A new glass series with nominal molar composition of 60B₂O₃ + 30NaF + 10Al₂O₃ co-doped with Dy³⁺ and Pr³⁺, synthesized by melt quench was reported. The influence of Rare Earth (RE) ratio variation on prepared glasses was investigated by using Fourier Transform Infra-Red spectroscopy, UV–Vis–NIR absorption spectroscopy, Photoluminescence, Decay curves and Density measurements. Their X-Ray Diffraction and FTIR spectra revealed the glassy nature and confirmed that AlO₆, AlO₄, BO₃ and BO₄ units are the main structural units of that matrix. A non-linear variation following the same trend for tetragonal borate units (N₄), Band gap, non-linear optical properties, Density, Molar Volume etc. was observed. Different optical parameters were obtained by UV–Vis–NIR spectroscopy. The Bonding parameter obtained from Nephelauxetic study indicated ionic nature of Dy³⁺ and covalent nature of Pr³⁺ ions. Photoluminescence excitation and emission spectra were recorded under variety of excitation wavelengths and corresponding color parameters were calculated using 1931 CIE standards. A detailed yellow to blue ratio analysis was reported as a function of RE ion concentration and excitation wavelengths. Composition DPNAB(x = 0.7) displayed the best performance with CIE coordinates (0.33, 0.37). Existence of Energy transfer from Dy³⁺ and Pr³⁺ was evidenced by the spectral overlap diagram and lifetime values obtained from fitting of Decay curves. From the obtained results, prepared glasses can be suggested for solid-state lighting devices like WLEDs and display devices.     

Intense broadband 3.1 μm emission in Er3+-doped fluoroaluminate-tellurite glass for mid-infrared laser application

Er³⁺ single doped fluoroaluminate-tellurite glasses were made by employing a conventional melt-quenching technique. A strong fluorescence around 3.1 μm was achieved from Er³⁺-doped fluoride glasses, under a 980 nm laser diode pump, which was assigned to the Er³⁺: ⁴S_3/2 → ⁴F_9/2 radiation transition process. The up-conversion and mid-infrared spectra of emission for fluoroaluminate-tellurite glasses with various concentrations of Er³⁺ ions dopant was researched. In addition, the calculated fluorescence lifetime value about 3.1 μm reaches 0.48 ms. The findings indicate that fluoroaluminate-tellurite glasses doped with Er³⁺ have prospects of being developed into 3.1 μm mid-infrared fiber and laser materials.