Effect of lead oxide on optical properties of Dy3+ ions in PbO–H3BO3–TiO2–AlF3 glasses

The effect of lead oxide (PbO) on optical properties of Dy³⁺-doped PbO–H₃BO₃–TiO₂–AlF₃ (LBTAFDy) glasses is investigated. The LBTAFDy glasses were prepared with different PbO contents ranging from 30 to 60 mol%. The Judd–Ofelt intensity parameters (Ω_{λ = 2, 4, 6}) are obtained by the least square fit analysis. It is found that the Ω₂ parameter and yellow-to-blue intensity ratio (Y/B) of the Dy³⁺ emission depend on the PbO content in LBTAFDy glass. The structural asymmetry around the Dy³⁺ ion and the DyO covalency are responsible for the changes in Ω₂ parameter and Y/B ratio. The variation of decay time of ⁴F_9/2 emission level with the PbO content also supports the changes in structural asymmetry and DyO covalency in LBTAFDy glass.     

Concentration dependence of Dy3+:1.3 μm luminescence in Ge–Ga–Sb–Se glasses

The Ge₂₅Ga₅Sb₅Se₆₅ glasses, doped with 0.01, 0.05, 0.1, 0.2, and 0.5 mol% of Dy³⁺ ions are prepared and the concentration dependence of Dy³⁺:1.3 μm luminescence is investigated. Remarkable energy migration between Dy³⁺ ions occurs as its concentration is more than 0.05 mol%. With further increasing amount of Dy³⁺ ions, the decay time of the 1.3 μm fluorescence decreases rapidly. All the decays are simple exponential and possible regimes of the donor decay are discussed.     

Compositional effects on fluorescence lifetime of Dy3+ ions embedded in chalcogenide Ge–As–S glasses containing very small amount of Ga and CsBr

We have investigated the fluorescence lifetimes of Dy³⁺: 1.3 μm emission in the chalcogenide Ge–As–S glasses with different compositions but identically containing 0.5 mol% Ga and 0.5 mol% CsBr. The measured lifetimes turn out to be sensitive not only to the concentrations of Ga and CsBr but also to compositional variations in the Ge–As–S host glasses. The lifetime is enhanced conspicuously in glass of the S-sufficient compositions, relative to the stoichiometric GeS₂–As₂S₃ composition, while this effect is not significant in the S-exact and S-deficient compositions. We employ Ga K-edge EXAFS analysis to support that the local structural environments of Ga in the modified chalcogenide glasses are closely correlated with the lifetime enhancement effect.     

Chemical characteristics of Dy–S bonds in Ge–As–S glass

From Dy L₃-edge extended X-ray absorption fine structure spectroscopic analysis of Dy-doped Ge–As–S glass, we verified that both the coordination number and Dy–S distance are decreased in this representative chalcogenide glass compared to those in the Dy₂S₃ crystalline counterpart. The strong covalent nature inherent in chemical bonds between the constituent atoms of Ge–As–S glass would be responsible for the enhanced covalency of the Dy–S bonds, which would then be sensitively related to the optical characteristics of the 4f ↔ 4f transitions of Dy³⁺ as well as the low rare-earth solubility exhibited by the Ge–As–S glass.     

Micro-structural studies of GeSe2–Ga2Se3–MX (MX = CsI and PbI2) glasses using Raman spectra

Microstructure of the chalcohalide glasses: GeSe₂–Ga₂Se₃–CsI and GeSe₂–Ga₂Se₃–PbI₂ ternary system were investigated by Raman spectra, lifetime of Dy³⁺ infrared emission and glass transition temperature (T_g). The evolution of the Raman spectra shows that the fundamental structural groups of these studied glasses consist of [Ge(Ga)Se₄] tetrahedral and some complex structure units [Ge(Ga)I_xSe_4?x](x = 1–4). The x value varied when the different iodide was added in Ge–Ga–Se matrix. For GeSe₂–Ga₂Se₃–CsI glasses, the [Ge(Ga)I_xSe_4?x](x = 1–4) mixed-anion tetrahedral and [Ga₂I₇]^? units occurred. For GeSe₂–Ga₂Se₃–PbI₂ glasses, the [Ge(Ga)I₂Se₂], [Ge(Ga)I₃Se] units can be formed. The changes of Dy³⁺ infrared emission lifetime and T_g support the results. Additionally, [PbI_n] structural units will be formed in GeSe₂–Ga₂Se₃–PbI₂ glasses due to high form-ability of these units when the PbI₂ content is high.     

Characterization of B2O3 and/or WO3 containing tellurite glasses

Characterization of B₂O₃ and/or WO₃ containing tellurite glasses was realized in the 0.80TeO₂–(0.20 ? x)WO₃ ? xB₂O₃ system (0 ≤ x ≤ 0.20 in molar ratio) by using differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectrometry techniques. Glasses were prepared with a conventional melt-quenching technique at 750 °C. To recognize the thermal behavior of the glasses, glass transition and crystallization temperatures, glass stability value, glass transition activation energy, fragility parameter were calculated from the thermal analyses. Density, molar volume, oxygen molar volume and oxygen packing density values were determined to investigate the physical properties of glasses. Fourier transform infrared spectra were interpreted in terms of the structural transformations on the glass network, according to the changing B₂O₃ and/or WO₃ content. Crystallization behavior of the glasses was investigated by in situ X-ray diffraction measurements and microstructural characterization was realized by scanning electron microscopy and energy dispersive X-ray spectrometry analyses.     

Design of Er3+-doped chalcogenide glass laser for MID-IR application

The feasibility of a photonic crystal fiber laser (PCF laser), made of a novel Er³⁺-doped chalcogenide glass and operating at the wavelength λ_s = 4.5 μm is investigated. The design is performed on the basis of spectroscopic and optical parameters measured on a fabricated Er³⁺-doped Ga₅Ge₂₀Sb₁₀S₆₅ chalcogenide bulk sample. The simulations have been performed by employing a home made numerical code that solves the multilevel rate equations and the power propagation equations via a Runge-Kutta iterative method. The numerical results indicate that a laser exhibiting slope efficiency close to the maximum theoretical one and a wide tunability in the wavelengths range where the atmosphere is transparent can be obtained.     

Fine embossing of chalcogenide glasses – a new fabrication route for photonic integrated circuits

For the first time embossing of ribs, from 1 to 10 μm wide and ∼10 mm long, has been carried out in chalcogenide glass layers sputtered onto semiconductor wafer substrates, with potential to act as monomode waveguides; these features have been similarly embossed in the surface of bulk chalcogenide glasses. The embossing shows very good replication of the GaAs mould patterning to 1 μm definition, with evidence also for sub-micron replication. For the embossing, thin coatings of the chalcogenide glasses were sputtered onto wafer substrates as follows: (i) a 6 μm layer of Ge₁₇As₁₈Se₆₅ (at.%) onto porous Si-on-Si wafer substrates and (ii) a 4 μm layer of Ge₁₅As₁₅Se₁₇Te₅₃ onto uncoated GaAs substrates. The Ge₁₇As₁₈Se₆₅ sputtered glass layer on porous Si-on-Si was demonstrated to slab waveguide at 1.55 μm wavelength; it was designed to achieve monomode waveguiding at 1.55 μm after embossing, for the 5 μm wide rib. The series of ribs, 1–10 μm wide, were successfully embossed in the Ge₁₇As₁₈Se₆₅ glass sputtered layer on porous Si-on-Si, but cracking of the glass layer occurred during the embossing process. Successful embossing of ribs without the glass layer cracking was achieved for the Ge₁₅As₁₅Se₁₇Te₅₃ sputtered glass layer on uncoated GaAs. Due to its relative simplicity, it is likely that hot embossing of this type of glass-based matrix offers an extremely promising route for producing high-resolution, guided-wave optical components and circuitry at low-cost, high-volume, and for a wide wavelength range.     

Glassy state and structure of Sn–Sb–Se chalcogenide alloy

The effect of Sn addition on the glass transition and structure of c-Sb₂₀Se₈₀ chalcogenide alloy have been studied by X-ray diffraction and differential scanning calorimetric studies. The increase in the glass forming region and the glass transition temperature with the addition of Sn is discussed by considering the formation of [SnSe₄] tetrahedra, another type of network former, which inhibits the crystallization. The differential scanning calorimetric studies on Sn_xSb₂₀Se_80−x (8 ⩽ x ⩽ 18) glassy samples reveal a single glass transition temperature for all values of x while a single crystallization peak was obtained only for 10 ⩽ x < 12. The X-ray diffraction studies reveal that the glass crystallizes to Sb₂Se₃ and SnSe₂ phases upon annealing. The glass formation and composition dependence of glass transition temperature in the Sn–Sb–Se chalcogenide alloy could be understood by considering the topological phase transitions and a chemically ordered network model.     

Time-resolved fluorescence measurements on Dy3+ and Sm3+ doped glasses

Various fluoride, phosphate and borosilicate glasses with known properties and global structure have been doped with Dy³⁺ (4f⁹) and Sm³⁺ (4f⁵) between 10¹⁸ and 10²¹ cm^?3 and their time resolved fluorescence in the visible range in combination with characteristic physical properties were studied. Different fit procedures were carried out. Although both ions differ in their intrinsic fluorescence lifetime, with 1.5 ms for Dy³⁺ and 6.5 ms for Sm³⁺, their dependence on glass matrix is remarkable similar. Fluoroaluminate glasses with varying phosphate content between 0 and 20 mol% (FPx), a pure phosphate glass (P100), and two borosilicate glasses with low (DURAN^®-like) and high optical basicity (NBS1) were used for investigations. A strongly ionic surrounding by fluorine ligands, as in fluoroaluminate glass samples, provides the longest fluorescence lifetime. It decreases with increasing phosphate content by increasing oxygen surrounding and with increasing RE³⁺ doping. Large differences were detected in the two borosilicate glasses depending on their optical basicity mainly due to differences in the Na₂O/B₂O₃ ratio. Duran-like samples with low Na₂O content have shown phase separation with higher doping concentration. The RE³⁺ ions are accumulated in the borate-rich droplets. Surprisingly only very low concentration-quenching effects were observed. In the opposite of NBS1 samples with high Na₂O content this generated extremely high quenching effect.     

Spectral studies of Sm3+ and Dy3+ doped lithium cesium mixed alkali borate glasses

The effect of host glass composition on the optical absorption and fluorescence spectra of Sm³⁺ and Dy³⁺ has been studied in mixed alkali borate glasses of the type 67B₂O₃ · xLi₂O · (32 − x)Cs₂O (x = 8, 12, 16, 20 and 24). The Judd–Ofelt intensity parameters (Ω₂, Ω₄ and Ω₆) are calculated. The radiative transition probabilities (A), radiative lifetimes (τ_R), branching ratios (β) and integrated absorption cross-sections (Σ) are computed for certain excited states of Sm³⁺ and Dy³⁺ ions for different x values in the glass matrix. Stimulated emission cross-sections (σ_p) are obtained for certain emission transitions of two ions in these mixed alkali borate glasses. These parameters are compared for different x values in the glass matrix. Variation of these parameters with x in the glass matrix has been studied.     

Glass forming region in the GeSe2–GeTe–PbTe system and some physicochemical properties of glassy alloys

New chalcogenide glasses from the GeSe₂–GeTe–PbTe system were synthesized. The glass forming region was determined using visual, X-ray diffraction and scanning electron microscopy analyses. It is extended towards the GeSe₂ and lies partially on the GeSe₂–GeTe (0–58 mol% GeTe) and GeSe₂–PbTe (20.0–57.5 mol% PbTe) sides. No glasses were obtained in the GeTe–PbTe system. The investigated physicochemical properties vary between 4.04–6.21 g/cm³ (density, d); 97–121 kgf/mm² (microhardness, HV); ?0.187 ÷ 0.007 (compactness, C) and 14.3–17.8 GPa (elasticity modulus, E), respectively.     

Luminescence behaviors of the Eu2+ ions in the GeS2-Ga2S3-CsCl chalcohalide glasses

In the paper, we report the luminescence behaviors of Eu²⁺-doped chalcohalide glasses. Composition of glass matrix is 37.5GeS₂-22.5Ga₂S₃-40CsCl (mol%) with the concentration of Eu²⁺ in the range of 0.1–0.25 (mol%). The optimal Eu²⁺ doping concentration was 0.15 mol% at which the glass exhibited an enhanced emission peaking at 434 nm with a full width at half maximum (FWHM) about 80 nm with the excitation at 395 nm.     

Luminescence and energy transfer in Dy3+/Tb3+ co-doped CaO–Al2O3–B2O3–RE2O3 glass

The new calcium aluminoborate glasses with the composition of CaO–Al₂O₃–B₂O₃–RE₂O₃ (RE = Dy and Tb) were synthesized and the luminescence of Dy³⁺ and Tb³⁺ was investigated. The results show that the emission intensity of Tb³⁺ ion was enhanced when introducing Dy³⁺ ion into CaO–Al₂O₃–B₂O₃–Tb₂O₃ glass due to the energy transfer processes between Dy³⁺ and Tb³⁺. The energy transfer efficiencies, transfer probabilities as well as donor–acceptor critical distances were also calculated. The energy transfer mechanism between Dy³⁺ and Tb³⁺ ions is electric dipole–dipole interaction, which can be concluded by both fluorescence decay and emission intensity ratio varieties.     

Electrodeposited and selenized CIGS thin films for solar cells

Cu(In,Ga)Se₂ polycrystalline thin films were deposited adopting the potentiostatic electrochemical method on Mo/soda lime glass substrate. All the as-deposited Cu(In,Ga)Se₂ thin films were annealed in a selenium atmosphere at 550 °C for 1 h to improve the film crystalline properties. The selenized CIGS thin films were characterized by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM).The results indicate Cu(In,Ga)Se₂ thin films have single chalcopyrite structure and the grain size varies from 0.8 to 2.5 μm.     

Optical properties of Pr3+ in selenide glasses modified with CsI

Effects of CsI content on the optical properties of Ge₃₀Ga₅Sb₅Se₆₀ glasses were evaluated. Linear and non-linear absorption properties of the glasses without Pr³⁺ were examined in addition to 1.6 μm emission properties of the Pr-doped glasses. Blueshift of the UV-side absorption edge was accompanied with increasing CsI concentration, while non-linear absorption coefficients measured at 1.06 μm by the Z-scan method remained unaffected. Measured lifetimes of the 1.6 μm emission from modified glasses were comparable to those of the unmodified glass. These experimental observations are discussed in connection with a pronounced weak absorption tail appeared in selenide glasses with the addition of CsI.     

Non-linear properties of chalcogenide glasses and fibers

High purity chalcogenide glasses were prepared in the series As₂S_(3?x)Se_x where x = 0 to 3. The measured third order non-linearities increase with the value of x, and are up to about 1000 times larger than silica for As₂Se₃ glass. We show that the anharmonic oscillator model, using the normalized photon energy, gives an excellent fit to the data over three orders of magnitude. Single mode optical fibers based on As₂S₃ and As₂Se₃ glasses have been fabricated using the double crucible technique and the Stimulated Brillouin Scattering (SBS) investigated. The threshold intensity for the SBS process was measured and used to estimate the Brillouin gain coefficient. Preliminary results indicate record high values for the figure of merit and theoretical gain, compared to silica, which bodes well for slow-light based applications in chalcogenide fibers.     

Luminescent properties and applications of Tb3+ doped silicate glasses with industrial scales

Tb³⁺ doped X-ray conversion glassy screen with an industrial scale (50 mm × 50 mm × 12 mm) was successfully fabricated, and its luminescent properties and applications in CCD imaging system were investigated. Results showed that Tb³⁺ doped silicate glasses mainly emit weak blue (400–460 nm) and strong green (480–570 nm) fluorescence. With the increase of Tb³⁺ ion concentration, the intensity of green emission increases, but that of blue emission decreases. Gd³⁺ ions can sensitize the luminescence of Tb³⁺ ions among silicate glasses. With the increase of CeO₂ concentration, the luminescent intensity of Tb³⁺ doped silicate glasses at 550 nm quickly decreases. However, the irradiation resistance of Tb³⁺ doped silicate glasses can be effectively improved by CeO₂ addition. The imaging quality of the luminescent glass screen is more excellent than that of Gd₂O₂S polycrystalline screens.     

Enhanced luminescent properties of Tb3+ ions in transparent glass ceramics containing BaGdF5 nanocrystals

Tb³⁺ doped transparent oxyfluoride glass ceramics containing BaGdF₅ nanocrystals were prepared. The transmission spectra, photoluminescence spectra, decay time and X-ray excited luminescence spectra of the Tb³⁺-doped glass and glass ceramics were investigated. Energy transfer from Gd³⁺ to Tb³⁺ has been observed in the glass and glass ceramics. The emission intensity of green band (⁵D₄ → ⁷F_J) of the Tb³⁺-doped glass ceramics is enhanced compared with that of the glass under ultraviolet and X-rays, which could be attributed to that the generation of BaGdF₅ nanocrystals with low phonon energy reduces the non-radiative transitions.