Photosensitivity of barium germano-gallate glasses under femtosecond laser direct writing for Mid-IR applications

Barium germano-gallate glasses are attractive glass hosts for photonic applications in the mid-infrared region up to 6 μm. In this work, we investigate the photosensitivity of such glasses under femtosecond laser, with an emphasize on the formation of refractive index changes. Six glasses with varying compositions (including addition of K, Na, Y, and La) were studied. We observed several transformation regimes in the pulse energy – repetition rate landscape: Type I (isotropic refractive index change) and a spatial broadening regime with a phase shift Δϕ > 2π rad at 550 nm. This translates into refractive index changes Δn > 10⁻² and is comparable to values obtained in most chalcogenide glasses. The effect of glass composition on Δϕ appears correlated to the number of non-bridging oxygen presented in the glass and is brought to evidence by monitoring the Cations/GaO_3/2 ratio. This provides a way to design a range of germano-gallate glasses suitable to imprinting high refractive index contrast.     

Integration Between Optical and Structural Behavior of Heavy Metal Oxide Glasses Doped with Multiple Glass Formers

Heavy metal oxide glasses (composition 60 PbO, 20 Bi₂O₃ mol%) and containing 20 mol% conventional glass formers SiO₂, B₂O₃, and P₂O₅ were prepared. Combined optical and Fourier transform infrared absorption spectra were measured for the prepared glasses to justify the role of glass formers in the optical spectra together with the network structural groups in such glasses. Also, the density and molar volume values were calculated to obtain some insight on the compactness and arrangement in the network. Optical measurements have been used to determine the optical band gap (E_g), Urbach energy (ΔE) and the refractive index (n). Optical spectra of all the samples reveal strong UV absorption which is related to the presence of unavoidable trace iron impurities (Fe ³⁺ ions) contaminated within the raw materials which were used for the preparation of the studied glasses. Additional near visible bands are observed in all prepared glasses due to characteristic absorption of Pb ²⁺ and Bi ³⁺ ions. Furthermore, The variations of the luminescence intensity, values of the optical band gap, band tail, and refractive index can be understood and related in terms of the structural changes that take place in the glass samples. The infrared absorption spectra of the prepared glasses show characteristic absorption bands related to the borate or silicate or phosphate network (BO₃, BO₄, SiO₄, PO₄ groups) together with vibrational modes due to Bi-O and Pb-O groups.     

Oxide ion/electronic polarizability,optical basicity and linear dielectric susceptibility of TeO2 – B2O3 – SiO2 glasses

A system of bio-silica borotellurite glasses was fabricated based on the chemical formula [(TeO₂)_0.7 (B₂O₃)_0.3]_1-x (SiO₂)_x with x = 0.1, 0.2, 0.3, and 0.4 using the melt-quenching technique using silica (98.548% SiO₂, from rice husk), TeO₂ (Alfar Aeser, 99.9%) and B₂O₃ (Alfar Aeser, 99.9%). Measurements and characterizations such as density and molar volume measurements, XRD analysis, FTIR, and UV–Vis spectroscopes were performed on the studied glasses. The objective was to determine the glasses’ applicability in optoelectronics, non-linear optics, and laser technologies through polarizability, linear electric susceptibility, and optical basicity study. Apart from confirming the amorphous nature of the glasses, the XRD analysis identified the presence of a crystalline phase of tellurium oxide (α-TeO₂) formed. The FTIR spectral study revealed the presence of TeO₃, BO₃, and SiO₄ structural units in the studied glasses. The refractive index (2.3026 – 2.2651), molar polarizability (8.0696 – 9.4334 Å³), oxide ion polarizability (3.2970 – 3.6202 Å³), electronic polarizability (0.2296 – 0.2335 Å³), dielectric constant (5.1307 – 5.3019), optical basicity (0.6719 – 0.7998), metallization criterion (0.410853 – 0.420714) and electric susceptibility (0.3286 – 0.3422 esu) of the glasses were presented. With the high refractive index and favourable electronic/oxide ion polarizability as well as good electric susceptibility, the glasses have shown great potential for optical fibre and laser applications. Metallization criterion value falls in the range of glasses with great potentials for non-linear optical application. The dielectric value suggests the glasses represent wideband semiconducting glasses believed to be good for application in microelectronic substrates fabrication.     

Optical properties,thermal stability,and forming region of high refractive index La2O3–TiO2–Nb2O5 glasses

The high refractive index La₂O₃–TiO₂–Nb₂O₅ glasses were prepared by containerless processing, and the glass‐forming region was determined. The refractive index showed the range from 2.20 to 2.32, and the values were much higher than those of most optical glasses. The completely miscible 30LaO_3/2–(70?x)TiO₂–xNbO_5/2 (0 ≤ x ≤70) system was fabricated to study the compositional dependence of refractive index and optical transmittance. The crucial determinants of the refractive index of oxide glasses, oxygen molar volume, and electronic polarizability of oxygen ions were calculated. The principle of additivity of glass properties was suitable for the calculation of refractive index between glass and compositional oxides. All the glasses were colorless and transparent in the visible to 6.5 μm middle infrared (MIR) region. These results are useful for designing new optical glasses with high refractive index and low wavelength dispersion in wide optical window.     

High Glass Transition Temperature Barium Silicophosphate Glasses Designed with Topological Constraint Theory

Alkali‐free glasses have attracted tremendous attentions for their high glass transition temperature (T_g). Such a feature broadens their potential applications, especially in the area of high‐density and high‐power laser glasses. BaO–P₂O₅ glasses, as one of the major matrix materials due to its high‐T_g, can be applied in high‐power laser glasses. Introducing SiO₂ is an effective method to improve the thermal, refractive index, and mechanical properties of phosphate glasses. Herein, we studied the barium silicophosphate glasses with MAS NMR and the T_g was successfully calculated by the topological constraint theory. The designed glass (20BaO–26.7SiO₂–53.3P₂O₅, mol%) with a high T_g (789K) was prepared and it also exhibited high refractive index and high Vickers hardness, suggesting the barium silicophosphate glasses have widespread applications in high‐power laser glasses and optical fibers.     

Thermal Stability,Optical Transmittance,and Refractive Index Dispersion of La2O3–Nb2O5–Al2O3 Glasses

La₂O₃–Nb₂O₅–Al₂O₃ high‐refractive‐index glasses were fabricated by containerless processing, and the glass‐forming region was determined. The thermal stability, density, optical transmittance, and the refractive index dispersion of these glasses were investigated. All the glasses were colorless and transparent in the visible to near infrared (NIR) region and had high refractive index with low wavelength dispersion. Some of these glasses were found to have significantly high glass‐forming ability. These results indicate that the ternary glasses are suitable for optical applications in the visible to NIR region. The effects of the substitution of Al₂O₃ for Nb₂O₅ on optical properties were discussed on the basis of the Drude–Voigt equation. It was suggested that the substitution of Al₂O₃ for Nb₂O₅ increased the molecular density and suppressed a decrease in the refractive index, even when both the average oscillator strength and inherent absorption wavelength decreased in La₂O₃–Nb₂O₅–Al₂O₃ glasses. These results are helpful for designing new optical glasses controlled to have a higher refractive index and lower wavelength dispersion.     

Certain Physical Properties of Binary Glasses Depending on Their Structural Specifics

The concept of structural elements, whose interaction determines glass properties, is used to interpret the regularities of the dependence of the refractive index in binary glass on glass composition, certain results of the mass-spectrometric analysis of the glasses vapor in the Rb₂O - B₂O₃ system, and the data on small angle x-ray scattering for glasses in the Na₂O - SiO₂ and Li₂O - SiO₂ system. Methods for estimating the refractive index of binary glasses depending on their composition and structure are proposed and examples of such calculations for alkali-silicate glasses are given.__________Translated from Steklo i Keramika, No. 1, pp. 8 – 11, January, 2005.     

The origin of the heterogeneous distribution of bismuth in aluminosilicate laser glasses

As one kind of novel and burgeoning laser materials, bismuth‐doped silicate glasses have aroused increasing attention for the super broadband near‐infrared (NIR) emission. However, the large optical scattering loss, resulting from optical heterogeneity in glass color and refractive index, limits their further applications in telecommunication system. Thus, it is urgent to uncover the essence of heterogeneity in Bi‐doped silicate glasses and subsequently improve glass optical performance. It will give us some hint to homogenize the glass component and Bi active centers so as to boost the development of Bi‐based glass materials. Here, taking 1 typical Bi‐doped calcium aluminosilicate glass as an example, we revealed the origin of the optical heterogeneities in glass color and refractive index through the NIR emission spectra, electron probe microanalyzer (EPMA) of elements and X‐ray photoelectron spectroscopy (XPS) of Bi 4f_5/2, Bi 4f_7/2, and Al 2p. The inhomogeneous distribution of Bi and aluminum components is responsible for the heterogeneity in this glass system. In addition, we found that tetrahedral coordinated aluminum favors the existence of Bi NIR centers, consequently resulting in enhanced Bi NIR emissions. Furthermore, based on our results and the role of Al³⁺ in glass network, we demonstrate the homogenizing of glass component by finely tuning glass composition. This work will enrich the understanding of Bi‐doped laser glass and provide a guideline for the design of component‐derived Bi‐doped silicate glasses and fibers with efficient NIR emission and high optical quality.     

Newly developed BGO glasses: Synthesis,optical and nuclear radiation shielding properties

In this research paper, we studied the optical and nuclear shielding efficiency of newly developed BGO glasses with the following compositions (in wt%): 32Bi₂O₃–68GeO₂, 42Bi₂O₃–58GeO₂, 47Bi₂O₃–53GeO₂, 52Bi₂O–48GeO₂, 62Bi₂O₃–38GeO₂. BGO glasses were prepared by traditional melt quenching method. To obtain the band gap values of fabricated BGO glasses, optical absorption spectra were used for evaluation of optical properties. The mass attenuation coefficients (μ/ρ) were achieved for prepared glasses at 0.015–15 MeV photon energies employing MCNPX Monte Carlo code and WinXcom program. Moreover, broad-range of nuclear shielding parameters for gamma ray, neutrons and charged particles such as mass attenuation coefficient, half value layer, effective atomic number, buildup factors, mass stopping powers, projected ranges, fast neutron removal cross sections and damage factors were calculated. The refractive index is calculated from E_opt, As Bi₂O₃ concentration is enhanced, E_opt is also increased as well as the optical electronegativity and consequently the refractive index. In addition, the results showed that BIGE5 glass sample with highest Bi₂O₃ contribution has excellent nuclear radiation shielding ability among the other fabricated glass samples.     

Increase in the refractive index of alkali titanium-hafnium silicate glass upon Na+ (glass)-Li+ (melt) ion exchange

An increase in the refractive index upon ion exchange in the Li₂SO₄ + Li₂MoO₄ salt melt has been studied for glasses of composition (mol %)xLi₂O-(25 -x)Na₂O-15TiO₂-6HfO₂-54SiO₂, wherex = 0, 5, 10, 15, 20, and 25. The ordinary transparent single-layer and two-layer diffusion zones are obtained. In the latter zone, the optically opaque near-surface layer gives way to a deeper optically transparent layer with the refractive index gradient. The opaque layer produced by the low-temperature exchange exhibits a unique structure, which is permeable to melt. An increase in the refractive index as large as 0.055 is achieved for the first time without fracture and crystallization of glass.     

Increase in the refractive index of alkali titanium-hafnium silicate glass upon Na+ (glass)-Li+ (melt) ion exchange

An increase in the refractive index upon ion exchange in the Li₂SO₄ + Li₂MoO₄ salt melt has been studied for glasses of composition (mol %)xLi₂O-(25 -x)Na₂O-15TiO₂-6HfO₂-54SiO₂, wherex = 0, 5, 10, 15, 20, and 25. The ordinary transparent single-layer and two-layer diffusion zones are obtained. In the latter zone, the optically opaque near-surface layer gives way to a deeper optically transparent layer with the refractive index gradient. The opaque layer produced by the low-temperature exchange exhibits a unique structure, which is permeable to melt. An increase in the refractive index as large as 0.055 is achieved for the first time without fracture and crystallization of glass.     

Phosphate glasses with improved optical properties

A study was undertaken to see how some components can affect the physicochemical properties of PbO−BaO−Al₂O₃−P₂O₅ optical glasses. The possibility is demonstrated for the manufacture of phosphate-base flint glasses with a high refractive index and improved transmission in the visible and UV regions of the spectrum. Translated from Steklo i Keramika, No. 2, pp. 3–5, February, 1997.     

Novel acousto-optic material based on Ge-Te-AgI chalcohalide glasses

A series of (GeTe_4.3)_100?x(AgI)_x (x = 5, 10, 15, 20, 25, 30 mol%) chalcohalide glasses was prepared to investigate their potential in acousto-optic (AO) materials. Detailed thermal and optical properties of these glasses have been analyzed by DSC, XRD and FTIR. Meanwhile, refractive index, density, elastic modulus, acoustic velocity and attenuation, and the AO figure of merit (M₂) were also reported. The results indicated that all these glasses presented a single glass transition temperature (T_g) and a single crystallization peak (T_x), and T_g decreases while T_x increases with the addition of AgI. X-ray power diffraction investigation showed the amorphous state of these synthesized glasses. They all have a wide transparent window from 2 to 20 μm, and acoustic attenuation was observed almost linearly proportional to the frequency at room temperature. Furthermore, refractive index and density increase, while acoustic velocity and elastic modulus decreases monotonously upon introducing AgI to GeTe_4.3. The maximum refractive index (n = 3.729) and minimum acoustic velocity (V = 2.037 × 10³ m/s) appeared in 70GeTe_4.3–30AgI glass, thereby resulting in a maximum M₂ of 3671 × 10^?15 s³/kg at 10.6 μm. The outstandingly high M₂ of this vitreous material make it attractive for far-infrared (FIR) AO modulators that require greater diffraction efficiency.     

Luminescence properties of Dy3+-doped alkali lead alumino borosilicate glasses

A new series of Dy³⁺-doped sodium lead alumino borosilicate glasses are prepared by the melt quenching technique with the chemical composition 20Na₂O- 10PbO-(5-x)Al₂O₃-40B₂O₃–25SiO₂-xDy2O3 (where x?=?0, 0.5, 1.0 and 1.5?mol%) and are characterized by various spectroscopic techniques such as XRD, FT-IR, Optical absorption spectra, Fluorescence spectra and Decay measurements. Optical and Luminescence spectra of all the glasses are recorded at room temperature. From the optical absorption spectra, optical band gap and Urbach energies of Dy³⁺-doped titled glasses have been evaluated. The oscillator strengths and the intensity parameters, Ω_λ (λ?=?2, 4 and 6) are calculated using Judd-Ofelt analysis. The various lasing parameters like transition probability (A_T), branching ratio (β_R), stimulated emission cross-section (σ_e) and the radiative lifetime (τ_rad) for different emission levels of Dy³⁺ ions have been evaluated. Fluorescence spectra show sharp emission peaks are observed at 482?nm (blue), 575?nm (yellow) and 665 (red) under 385?nm excitation, which are attributed to ⁴F_9/2→⁶H_15/2, ⁶H_13/2 and ⁶H_11/2 transitions respectively. The yellow-to-blue intensity ratio (Y/B) increase up to 1.0?mol% Dy³⁺ ion content and beyond it decreases because of concentration quenching which occurs due to the energy transfer between Dy³⁺ and Dy³⁺ ions. The x, y coordinates of the prepared glasses pass through the white light region in the CIE 1931 chromaticity diagram. The results reveal that these glasses emit quality white light which is suitable for the development of W-LEDs. The color purity and the correlated color temperature (CCT) are also calculated for the present work. Various physical parameters such as density, refractive index, and ion concentration etc., are calculated. Among the prepared glasses, NPABSDy10 glass exhibits higher σ_e, β_R, σ_exτ_R, and σ_exΔλ_eff values corresponding to the ⁴F_9/2→⁶H_13/2 emission band and these are in turn specifies its suitability for W-LEDs and visible laser applications.     

Formation and stability of glasses with ultra-optical properties in TiO<Subscript>2</Subscript>–Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–PbO system

To obtain ultra-optical property in glasses, as the basis for photonic applications, the glass forming region of TiO₂–Bi₂O₃–PbO system was investigated and determined by melting series of compositions in the system. The glass-forming boundary region was defined. The best compositions for glass formation were found to be around the eutectic and peritectic regions in the corresponding phase diagram. Generally, stability increased with the addition of TiO₂, acting as a conditional glass former, to a maximum of 15TiO₂ mol %. Replacing PbO with Bi₂O₃ in the glass worsened the stability, due to the increase of heavy cation Bi^3– in the glass structure. Finally, the refractive index and dispersion of some stable glasses were measured, which were as high as 2.435 and 10.2, respectively.     

Effect of substrate temperature on the properties of TiO2 nanoceramic films

TiO₂ nanoceramic films were deposited on glasses by rf magnetron sputtering. This method provides more advantages in controlling the microstructure and composition of the films. TiO preferentially formed and the deposited films tended to become nonstoichiometric by increasing substrate temperature. The morphologies and hydrophilic properties of TiO₂ films were significantly affected by the substrate temperature. The nonlinear refractive index of the TiO₂ film on the glass substrate measured by Moiré deflectometry was of the order of 10^?8 cm² W^?1. Smaller grain size, higher optical energy gap, visible transmission and linear refractive index, and lower stress-optical coefficient were obtained at lower substrate temperature.     

REFRACTIVE INDICES OF SOME GLASSES IN THE TERNARY SYSTEM K2O 4SiO2-Fe2O3-SiO2*

In the course of some phase-rule investigations of the ternary system K₂O-4SiO₂-Fe₂O₃-SiO₂ by the “quenching method” of Shepherd, Rankin, and Wright, the refractive indices of 30 glasses were measured by the usual petrographic immersion method. The refractivities varied from 1.438 for a K₂O-7SiO₂ glass to 1.621 for the most ferriferous glass which contained 32.3% Fe₂O₃. The maximum FeO content reached a value of 0.33 % in a glass originally containing 25 % Fe₂O₃. Along the sections K₂O 4SiO₂, K₂O-5SiO₂, K₂O-6SiO₂, and K₂O-7SiO₂, the relation between the Fe₂O₃ content of the glasses and the refractive index is apparently linear. The isofracts, however, in the ternary system are curved lines.     

Microscopic Origins of Compositional Trends in Aluminosilicate Glass Properties

Revealing and understanding the microscopic origins of the macroscopic properties of aluminosilicate glasses is important for the design of new glasses with optimized properties. In this work, we study the composition‐structure‐property relationships in 20 MgO/CaO sodium aluminosilicate glasses upon Al₂O₃‐for‐SiO₂ and MgO‐for‐CaO substitutions. We find that some properties (density, molar volume, Young's modulus, and shear modulus) are linear through the investigated range of Al₂O₃ compositions, while others (refractive index, coefficient of thermal expansion, Vickers hardness, isokom temperatures, and liquid fragility index) exhibit a change in the slope around the composition with [Al₂O₃] = [Na₂O], which is especially pronounced for the glasses containing MgO. We discuss these phenomena based on structural information obtained by NMR spectroscopy and topological considerations.     

Effect of iron oxide (Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>) on the structural,optical, electrical,and dielectric properties of SrO–V<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

The oxide glass system of the composition (10 – x)SrO–xFe₂O₃–90V₂O₅, (x = 0, 2, 4, 6 and 8 mol %) were prepared by a standard melt quenching technique. The amorphous nature of the prepared glass was confirmed using X-ray diffraction technique. The infrared spectra of these glasses were recorded over a continuous spectral range (850–1500 cm^–1). The density of prepared sample was obtained by the Archimedes principle. The physical parameters of the glasses were also determined with respect to the composition. Density increases from 3.10 to 3.20 g/cm³, whereas the molar volume decreases with the increase in Fe₂O₃ concentration. In order to study optical properties, absorption spectra were measured at room temperature. Indirect optical energy band gap, optical dielectric constant, refractive index were calculated from optical energy band gap. The refractive index decreases gradually with the increase in Fe₂O₃ content due to increase of bridging oxygen’s. For temperatures from 300 to 500 K, the dc conductivity increased with the increasing Fe₂O₃ content. The dielectric properties like dielectric constant, dielectric loss factor and dielectric loss tangent investigated at the room temperature in the frequency range of 10 kHz to 1 MHz decreases with frequency. The dielectric behavior shows strong frequency as well as composition dependence.     

Investigation of the Electrode Properties of Glasses as a Method for Elucidating the Structural Role of Their Components: The 25Na2O–15TiO2–6ZrO2–4RxOy–50SiO2 System (R = Ca, Ba, Sr, La, Nb, and Ta)

Glass electrodes are fabricated from the title glasses, and the emf–pH curves are measured at room temperature. The structural role played by the glass components is elucidated from an analysis of the curves. The TiO₂, ZrO₂, Nb₂O₅, and Ta₂O₅ oxides are network-formers, and their effect on the electrode properties of glasses upon simultaneous introduction is summarized within the limits of the studied compositions, whereas the total acidity of the glass increases. The oxides of modifiers La, Ba, Sr, and Ca neutralize the acidic groups of the network-former (supposedly [ZrO_6/2]^2–). The tendency to neutralization decreases in the above order. The ionic electrode selectivity of glasses with an increased content of ZrO₂, which contain Nb₂O₅ and Ta₂O₅, is expressed by the series H⁺ Na⁺ > Li⁺ > K⁺.