Optical properties of Tm3+ ions in alkali germanate glass

Tm-doped alkali germanate glass is investigated for use as a laser material. Spectroscopic investigations of bulk Tm-doped germanate glass are reported for the absorption, emission and luminescence decay. Tm:germanate shows promise as a fiber laser when pumped with 0.792 μm diodes because of low phonon energies. Spectroscopic analysis indicates low non-radiative quenching and pulsed laser performance studies confirm this prediction by showing a quantum efficiency of 1.69.     

Raman spectra and thermal analysis of a new lead–tellurium–germanate glass system

Differential scanning calorimetry (DSC) and Raman scattering studies of a new glass system, lead–tellurium–germanate glasses in the form of (90−x)GeO₂·xTeO₂·27PbO·10CaO with x=0, 10, 20, 30, and 40, are reported. The glass samples were fabricated using a conventional melt-quenching method. The Raman spectra and possible glass structures are discussed for different TeO₂ contents. The results indicate that increasing TeO₂ content up to 40 mol% in the glass system decreases the glass transition temperature and melting temperature, and suppresses the crystallization tendency in the fiber pulling temperature range. The lead–tellurium–germanate glass, GTPC, possesses a larger refractive index and a smaller maximum phonon energy than that of a lead–germanate glass, 63GeO₂·27PbO·10CaO, and shows a better thermal stability compared to a tellurite glass, 75TeO₂·20ZnO·5Na₂O (TZN). These improved properties could be beneficial for fabricating rare-earth doped fiber devices.     

Photosensitive erbium doped tin-silicate glass

Erbium doped tin-silicate samples were prepared by sol-gel method. Optical absorption, infrared photoluminescence at 1.5 μm from ⁴I_13/2-⁴I_15/2 Er³⁺ electronic transition and data of refractive index change after exposure to 266 nm pulsed radiation were collected. The results show that Er-doped tin-silicate can be produced by the proposed sol-gel method with photosensitivity comparable to that of only tin-doped silica, showing refractive index changes up to 4×10⁻⁴.     

Raman and optical reflection spectra of germanate and silicate glasses

Germanate and phosphosilicate glasses made in oxygen surplus conditions were studied by Raman and optical reflection methods. We found that the optical reflection spectra of the germanate glasses are quite similar to the one those of a GeO₂ crystal with the α-quartz structure. The reflection of phosphosilicate glasses is very close to silica glass-related spectra. Hence, the determining influence of the tetrahedral structure on reflection spectra is revealed. The Raman spectra of germanate samples are similar to those reported the one known in the literature. Octahedral entities, namely bands similar to stishovite vibration modes, were difficult to detect in phosphosilicate glasses through Raman spectroscopy.     

Optical properties of bismuth in germanate,borax and phosphate glasses

Absorption, emission, excitation spectra and quantum efficiencies of luminescence of bismuth were obtained in germanate, borax and phosphate glasses. Decay times were measured for fluorescence of bismuth in germanate glass at room temperature and liquid air temperature. A non-exponential decay of fluorescence at room temperature is observed. A thermal equilibrium between the ³P₁ and ³P₀ states is discussed. The dependence of fluorescence intensity and decay times on temperature is presented. The amount of covalency between bismuth and glass matrix was calculated from the nephelauxetic effect.     

Optical absorption and photoluminescence studies of Nd doped alkali boro germanate glasses

Optical absorption and photoluminescence studies have been carried out at room temperature in 25 R₂O-25 GeO₂-49.5 B₂O₃-0.5 Nd₂O₃ glass systems, (Composition in mol%, R = Li, Na, K and Rb). Judd Ofelt Intensity parameters and other parameters like Racah (E¹, E² and E³), Slater-Condon-Shortley (F₂, F₄ and F₆) Spin-Orbit Coupling (ξ_4f) and Configuration Interaction (α,β and γ) for Nd³⁺ ion in the glass system are calculated. The variation of the Ω₂ parameters are interpreted in terms of the covalency of the RE ion in the glass matrix. Further the hypersensitive transition ⁴I_9/2 → ⁴ G_5/2, ² G_7/2 is analyzed with respect to the intensity ratio I_L/I_S and is found to be dependent on the type of alkali in the glass matrix. The Photoluminescence studies do not show any appreciable shift in the peak emission wavelength of the ⁴ F_3/2 to ⁴I_11/2 transition with the change in alkali type.     

Optical spectra of glasses

This presentation focuses on several ways in which structural and dynamical information can be obtained from optical spectroscopy by examining results of infrared and Raman studies of selected oxide glasses. Though these studies represent only a small fraction of the work on most of the glasses mentioned, and many other important forms of optical spectroscopy are not treated here, they illustrate useful approaches to the study of amorphous materials by optical methods.     

Mixed alkali glass spectra and structure

The far infrared and Raman spectra of several series of mixed alkali metaphosphate glasses have been investigated as a function of the mole fraction x of the network-modifying ionic oxides in xM₂O(1?x)M₂′O · P₂O₅. The frequencies of the cation-motion bands in the far infrared spectra, which correspond to cationsite vibrations, do not shift with x, indicating that the vibrationally significant local geometry and forces associated with a particular cation are unaffected by the introduction of the second cation into the glass structure. Each Raman-active band due to vibrations of the metaphosphate network occurs at a different frequency for each pure glass (x = 0 or 1), but for mixed alkali glasses only one band occurs for each type of mode and it varies linearly with x. This indicates that the cations in these mixed alkali glasses are homogeneously distributed, there is no significant molecular-level domain formation and the phosphate chains are associated with an averaged cation environment whose effect on the chain modes varies with x. A simple vibrational model is presented which shows that the cation-dependent shifts are due to small changes in network bond angles and variation of the cationsite forces.     

Singular-value decomposition and boron NMR spectra in glass

We have applied the method of singular-value decomposition to the analysis of boron NMR spectra in glass. This procedure, which is useful for handling least-squares problems, clearly shows that there are a large number of solutions to any boron NMR spectral analysis problem. This limits the technique as a structure tool.     

Optical and lasing properties of fluorophosphate glass

Neodymium-doped fluorophosphate glass is a laser material newly-developed for use in high power laser fusion systems. The low refractive index (n_d ～ 1.45) and low dispersion (Abbe number ～90) of fluorophosphate glasses give them the properties of low nonlinear refractive indices and long Nd³⁺ fluorescence lifetimes, which are desirable for the high power laser applications. We have measured the intensity gain of 1.052 and 1.064 nm laser light produced by flashlamp-pumped fluorophosphate glass amplifiers, varying in size from 4–34 clear aperture. The measured gains are compared with those measured in other laser glass types and with those predicted from the spectroscopic properties of Nd³⁺. We estimate that the peak cross section for the ${}^4\text{F}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{→}{}^4\text{I}{}_{\mathrm{<mtext>11</mtext><mtext>12</mtext>}}$ transition in commercial fluorophosphate laser glasses is ～2.2 × 10^?20 cm².     

Universal properties of high-frequency spectra in glass formers

The vibrational spectra of glass formers follow different laws with respect to crystals. A rationale for their anomalous behavior is provided by the euclidean random matrix theory. Experiments on glass formers at different densities might be a suitable route to test the prediction of the theory.     

Systematic study of spectroscopic properties and thermal stability of lead germanate glass doped with rare-earth ions

Glasses with composition 50GeO₂–(50?x)PbO–5PbF₂–xLnF₃ (Ln = Pr³⁺–Yb³⁺) were prepared from commercial raw materials. The content of PbF₂ was constant and amounted to 5 mol% whereas the concentration of luminescent ions was diverse (0.2 and 2 mol%). Thermal stability of the glasses were monitored by differential thermal analysis (DTA). It has been found that increase of rare-earth fluoride content from 0.2 mol% to 2 mol% brings about a shift of the glass crystallization onset from 450 °C to 487 °C for Nd-doped samples and from 466 °C to 482 °C for Tm-doped samples. Optical absorption and emission spectra of Ln active ions in oxyfluoride glass have been investigated at room temperature in the ultraviolet (UV), visible (VIS) and near-infrared (NIR) region. Oscillator strengths, phenomenological Judd–Ofelt intensity parameters Ω_2,4,6, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels have been estimated. Analysis of decay curves of luminescence revealed that the increase of rare-earth fluoride content from 0.2 mol% to 2 mol% shortens the lifetime of the ⁴F_3/2 level of Nd³⁺ from 224 μs to 90 μs.     

Time-resolved fluorescence spectra of titanium-containing fluorophosphate glass

The visible luminescence due to Ti³⁺ ions in titanium-containing fluorophosphate glass has been observed with UV excitation. Time-resolved fluorescence and lifetime measurements have also been performed at room and low temperature, respectively.     

Optical spectra of sodium phosphate glasses

The visible, infrared, and ultraviolet spectra of seven glasses in the Na₂OP₂O₅ binary system were obtained. Changes in spectra were related to structural changes occurring the glass. Dopant ions Co²⁺, Cu²⁺, and Pb²⁺ were used to infer structural changes occurring as the metaphosphate composition was crossed going from pyrophosphate compositions into ultraphosphate compositions. The presence of chemically bound water was found to cause the overall modifier-to-former ratio to remain constant for glasses containing greater than 65 mol.% P₂O₅.