In glasses, even low levels of dopants or impurities can give rise to very intense and broad charge transfer transitions from ligands (e.g. oxygen or fluorine ions) to the metal ion (L→M), absorbing strongly in the short wavelength ultraviolet. In an attempt of a systematic review of charge transfer transitions, we compile data of various glass systems with high intrinsic transmission that allow the observation of charge transfer (CT) transitions involving cations of different electronic configurations. Various glasses of different composition were selected as matrices, including fluoroaluminate glasses with low P2O5 content (FP10 = 35AlF3–10MgF2–30CaF2–15SrF2–10Sr(PO3)2), phosphate [SrP = Sr(PO3)2, NSP = Na2O-40SrO-50P2O5], silicate (NS = 15Na2O–85SiO2, DS = 33Na2O–67SiO2), aluminosilicate (BCAS = 10BaO–10CaO–15Al2O3–65SiO2) and borosilicate (NBS1 = 16Na2O–10B2O3–74SiO2, NBS2 = 4Na2O–1Al2O3–21B2O3–74SiO2, Duran = 5Na2O/K2O–1Al2O3–12B2O3–82SiO2) compositions. All glasses were prepared from very high purity materials and doped with various metal ions. Charge transfer transitions of electrons to or from these cations induce absorption and photoluminescence phenomena in the ultraviolet and visible spectral region, which were recorded by optical spectroscopy. Charge transfer transitions were considered for empty valence orbitals, that is, for the high valent 3d, 4d and 5d ions, and for Zn2+, Ag+, Cu+ with full d10 orbitals. 3d, 4d and 5d ions with partially filled valence orbitals that could be stabilized in the named glasses are studied as well. Doping concentrations for these allowed transitions typically ranged from 5 to 5000 wt-ppm of metal ions, with some samples also displaying higher dopant levels. Inter valence charge transfer (IVCT) transitions directly from one metal ion to a neighboring metal ion (M→M) of the same element or metal to metal charge transfer (MM-CT) between ions of different elements can also induce strong visible absorption and deep coloring for which some examples will be discussed.

The influence of Eu3+, Eu2+ and Tb3+ ions on x-ray and ultra violet laser induced defects is examined in a fluoride phosphate and an ultraphosphate glass. The defects are characterised by optical absorption, fluorescence and ESR spectroscopy Europium ions cause larger changes in the fluoride phosphate glass whereas terbium ions do in the ultraphosphate glass. Different mechanisms of defect formation are found for x-ray and ultraviolet excimer laser irradiation at 248 nm. X-ray irradiation induces valence changes of a part of the dopant ions into (Eu3+)-, (Eu2+)+ and (Tb3+)+ ions, respectively: By contrast, laser irradiation results in a very hst and complete photo-oxidation of Eu3+ but in a very slight photooxidation of Tb3+. Photoreduction of Eu3+ does not occur. Under x-ray irradiation, the dopants have a similar but small influence on the intrinsic defect formation. Extrinsic rare earth related defect centres replace intrinsic defects. On the contrary the laser induced photo-oxidation of Eu2+ enhances considerably the amount of intrinsic electron centres but suppresses effectively the formation of intrinsic hole centres. However; Tb3+ doping increases both electron and hole centre formation. These peculiarities of Eu2+ and Tb3+ doping result from the coincidence of the laser energy with the 4f-5d transitions of the rare earth ions. The fast and intense laser induced defect formation in the Eu2+ and Tb3+ doped glasses suggests that these dopants are promising candidates for increasing the photosensitivity of glasses.

Various borate and borosilicate glasses doped with Tb3+ in a broad concentration range of 1 x 10(18) to 1 x 10(21) Tb3+ per cm(3) (~0.01 to 10 wt% Tb2O3) were prepared and characterized by different methods. Static fluorescence excitation and emission spectra of Tb3+ in the ultraviolet-visible range were recorded. The fluorescence decay rates of the green emission were measured and fitted. Different lifetimes dependent on different local sites of Tb3+ ions were detected. To identify these different local sites crystalline terbium borate, TbBO3, was prepared and investigated. X-ray diffraction (XRD) and electron microscopy measurements were used. Very strong clustering effects of Tb (3+) ions were detected as preliminary stage of phase separation by formation of a very short decay rate in optically clear borate containing glasses with low optical basicity. In glass samples with phase separation, the Tb3+ ions were accumulated in the phase with higher optical basicity. The local sites of the Tb3+ ions in the clusters induce a short lifetime which is similar to the lifetime of crystalline TbBO3. Only mono-exponential decay curves for Tb3+ fluorescence were detected in sodium borosilicate glass with high optical basicity, and in zinc borate glass, without tendency to phase separation.

The local structure of the model glasses (NaPO3)(1-x)(AlF3)(x) (0 <= x <= 0.4), prepared by standard melt-cooling, was extensively investigated by high-resolution solidstate nuclear magnetic resonance (NMR) including advanced double-resonance techniques. This glass system offers the opportunity of studying five different heteronuclear distance correlations (Na-F, Na-P, P-F, Al-F, and P-Al) by 10 distinct double-resonance experiments, involving all of the constituent elements present. Al-27 MAS-NMR data indicate that aluminum is predominantly six-coordinated. According to Al-27{P-31} and Al-27{F-19} rotational-echo double-resonance (REDOR) spectroscopic results, two to three Al-F and three to four Al-O-P linkages occur in these glasses, independent of composition x. F-19 MAS-NMR spectra show the presence of terminal P-bound and Al-bound fluorine species. A small amount of fluorine bridging to two aluminum octahedra, which could be assigned based on F-19{Al-27} and F-19{P-31} REDOR experiments, was also detected. F-19{Na-23} REDOR experiments indicate that the Al-bound terminal F atoms interact significantly more strongly with sodium ions than the P-bonded terminal F atoms, which is consistent with local charge considerations. On the basis of the detailed quantitative dipole dipole coupling information obtained, a comprehensive structural model for these glasses is presented.

Phosphate glasses are of great interest for basic research and for special applications in various fields as technical and optical glasses. Metaphosphate compositions with PO4-chain structure are mostly used. The cations have a significant effect on the properties of the glasses and melts. This was studied in more details. High purity metaphosphate glasses, M-n(PO3)(n) with M = Na+, K+,Zn2+, Mg2+, Ca2+, Sr2+, Ba2+, Al3+ and Fe3+, were prepared and the optical and thermal properties were measured with different methods. The electrical conductivity of glasses and melts is the property of great practical importance. It was determined by impedance spectroscopy in a wide temperature range from 300 to 1250 degrees C in frequency range of 0.1Hz to 6 MHz. The electrical conductivity of alkaline earth phosphate glasses and melts increases with increasing ion radius of the cation. NaPO3 and KPO3 glasses and melts have much higher conductivity. Viscosity measurements were carried out from transformation temperature, T-g, to the melt. The measured data were fitted and the activation energies of the conductivity and viscosity were calculated. Simple exponential behavior was found at temperatures below T-g, but above T-g, only in very narrow temperature range. The relation between conductivity and viscosity was considered.

Abstract Materials with high deep-ultraviolet (DUV; λ<300 nm) transmission are important for many industrial applications. Fluoride single crystals and various glasses, pure SiO2, fluoride, phosphate, multicomponent silicates, and organic materials (PMMA), were investigated. The role of intrinsic absorption (UV edge) due to electron transitions between the main components, and extrinsic absorption due to trace impurities, effect of polyvalent ions, redox behavior, and radiation-induced transmission loss were considered. The optical basicity and optical properties were used to order the materials.

Four glass series with identical nominal composition of (100-x)NaPO3-xAlF3 (NAPF), with x = 0 to 40 mol %, were prepared by melting under different conditions and are compared here for their compositional and structural variations. Melting these glasses at different temperatures, with or without a crucible lid, with or without an additional fluorinating agent (NH4 HF2 or NH4F) and with different quality of the raw materials (OH content) was found to determine fluoride retention. In addition, melting in alumina crucibles can change the glass composition through Al2O3 uptake from the crucible, which does not happen to melts prepared in Pt crucibles. Glasses of the differently prepared series were investigated for their actual composition and in regard to structural variations using Raman and also solid-state NMR spectroscopy. The glass density increases for all series in a similar manner with increasing fraction of AlF3. The glass transition temperatures Tg vary by up to 100°C between nominally similar glasses prepared under different conditions. A higher Tg is generally observed for higher aluminum content and lower fluoride levels. Thus, glasses melted in Al2O3 crucibles have the highest F-loss and showed the highest Tg values. The effect of the melting temperature is reflected in the number of P-F bonds which break up in NAPF glasses above 850°C, while Al-F bonds are more stable.

In an earlier review((1)) we discussed the connectivity in borosilicate glasses and compared our experimental findings by NMR, infrared and Raman spectroscopies with older structural models. We could show, contrary to the often cited reedmergnerite type model, that a significant preference exists in low alkali borosilicate glasses for trigonal rather than tetrahedral borate groups to link to silicate entities. Another often cited misconception is the application of the Loewenstein rule to borate tetrahedra. While linking of two "[Alempty set(4)](-) tetrahedra is disadvantageous compared to higher coordinated aluminate polyhedra, the borate tetrahedral units represents already the alternate higher coordination state and accordingly, many examples of linked [Bempty set(4)](-) tetrahedra are known to exist in glasses as well as in crystalline compounds of boron at normal pressure conditions. We now present more NMR data on three different low alkali borosilicate glasses with Na2O:B2O3=02 to 035 and decreasing SiO2 fractions (74 to 43 mol% SiO2), for which we compare variations in the near and intermediate range structure of quenched and slowly annealed samples. None of the studied glasses showed a significantly higher fraction of trigonal Bempty set(3) groups in the quenched than in the annealed samples, even though borate in the three-coordinated state is the preferred metaborate unit in the melt. However, for the two silicate rich glasses (including NBS 2), we observe at low temperatures a deviation of the viscosity-temperature plot from the ideal VFT-fit, that is from T-g at circa 440 to the expected 600 degrees C. For samples prepared at any annealing temperature below 600 degrees C, structural variations with thermal history are apparent, and are also reflected in many glass properties including density, fracture probability, or refractive index. Even though the glass NBS 2 shows no visible phase separation, DSC measurements indicate the presence of two different T-g values corresponding to the borate and the silica rich subnetworks. The values of the two T-g events shift with different cooling rates: for fast quenched glasses the two T-g values are closer together than for slowly annealed glasses. The study of these low alkali borosilicate glasses is ongoing, as we understand better how structural variations with changing thermal history impact the glasses' properties. Analogously, we can apply the same techniques to follow structural variations under external forces, such as irradiation, laser modification, pressure and mechanical impact.

Single crystals of three oxide compounds containing stoichiometric Nd, doped with Yb3+ ions, namely K5Nd(MoO4)(4) (KNM), RbNd(WO4)(2) (RNW), and NdAl3(BO3)(4) (NAB) were grown from melts using Czochralski method or top seeded solution growth technique. Nd3+ fluorescence characteristics were measured in dependence of Yb3+ content and temperature. It was established that increasing Yb3+ content results in a decrease of the Nd3+ lifetime. However, the corresponding decay times values were quite different and varied from 9.5 mu s for NAB up to 60 mu s for KNM and 3.3 mu s in RNW. Judd-Ofelt theory was applied to estimate the intrinsic lifetime of the F-4(3/2) emitting level of Nd3+ for all three crystals. The calculated lifetime values are much higher than the measured values. This effect is attributed to the strong concentration quenching of the Nd3+ ions due to their high concentration in all three crystals. The possible mechanisms of the observed dependences are given. (C) 2015 Elsevier B.V. All rights reserved.

Our investigations of phosphate and fluoride phosphate optical glasses started in 1976. The aim was the development of optical glasses with high positive anomalous partial dispersions, making them desirable for lens designs that reduce the secondary spectrum in high performance optics to substitute for CaF2 single crystals. A large variety of glasses have been prepared and investigated. The effect of cations and fluorine in phosphates on the refractive index, dispersion, thermal and chemical properties was studied. It was found that fluoride phosphate glasses based on AlF3, MF2, and P2O5, have the required optical properties. Fluor crown and phosphate crown optical glasses were developed. The structure and properties of these glasses depend mainly on the molar relation between fluorides and phosphates, which can be varied in a wide range between pure fluoroaluminate and phosphate glasses. The structure model can be described as chains of Al(F,O)(6) octahedra, bonding by mono- and diphosphate groups and cations. Their intrinsic transparency in the vacuum UV range is comparable with those of silica, and CaF2. The absorption coefficients of possible trace impurities in different redox states were determined. The effect of UV lamp, UV laser, x-ray radiation, and laser writing of waveguides was studied. Together with colleagues from physics departments, we developed efficient laser and amplifier glasses with Nd3+, Er3+, and Yb3+. The POLARIS (petawatt optical laser amplifier for radiation intensive experiments) system is based on a fluoride phosphate glass doped with Yb3+, which is used as the active medium, pumped by light from laser diodes. Photoluminescence in glasses doped with ions in s(2) configuration (Sn2+, Pb2+, As3+, Sb3+), d(0) configuration (Te4+, Nb5+, Ta5+, Mo6+, W6+), or d(10) configuration (Ag+, Cu+), which absorb strongly in the UV, has been demonstrated mainly in the UV and blue-green region. Efficient visible photoluminescence with different lifetimes was found in Mn2+ (3d(5)), and in rare earth (f(n)) doped glasses (Ce3+, Pr3+, Sm3+, Eu2+, Eu3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+), which can be used for various applications.

Structural, optical, and physical properties of glasses prepared by melt reduction in the mixed Sr-Mn metaphosphate system xMnO-(1 - x)SrO-P2O5, 0 <= x <= 1, have been investigated by vibrational, optical, EPR, and thermal techniques. Mn ions were found mostly in the +2 oxidation state and in sites of octahedral symmetry. Such sites are formed by neighboring Mn-oxygen polyhedra, where the covalent character of Mn-O bonding increases with cation mixing. The phosphate structure was found to consist predominantly of metaphosphate tetrahedral species (Q(2)) with a minority of pyrophosphate (Q(1)) and neutral (Q(3)) phosphate tetrahedra, whose relative abundance changes nonlinearly with MnO content. The symmetric stretching vibration of terminal PO2- units in Q(2) species was employed to probe the influence of mixed Sr/Mn environments on phosphate structure, and the results suggested a deviation from the homogeneous distribution of metal cations. This was attributed to the coordination numbers of Sr and Mn ions (i.e., 8 and 6, respectively) which exceed the available number of terminal oxygen atoms per metal ion, M (i.e., 4), and thus require the formation of neighboring M-oxygen polyhedra which are connected by P-O-M-O-M-O-P linkages. Nevertheless, each metal ion was found to form its own M-O site and to retain the identity of its site in both single and mixed cation glasses. While density and molar volume follow a linear decrease with MnO content, glass transition temperature T-g, thermal expansion coefficient, refractive index, and optical dispersion exhibit clear deviations from additivity. The increasing trend of T-g with cation mixing was attributed to a combination of the different cross-linking abilities by P-O-M-O-M-O-P bridges of the Sr and Mn ions with the relative proportion of metaphosphate Q(2) units. The composition dependence of optical dispersion, as expressed by the Abbe number, was correlated with the average electronic band gap obtained from refractive-index dispersion data using the Wemple-DiDomenico single oscillator model. While all glasses in the Sr-Mn system were found to exhibit low optical dispersion, cation mixing was shown to increase dispersion because of increased covalency in Mn-O bonding.

The coordination and bonding of Mn2+ ions in glasses can be probed sensitively and selectively by electron paramagnetic resonance (EPR) and photoluminescence spectroscopy. These methods also give information on Mn-Mn ion interactions and cluster formation. Mn2+ ions were found to be tetrahedrally coordinated in borosilicate glasses of high optical basicity, and octahedrally coordinated in low alkaline borosilicate glasses (Duran-type) as well as in binary borate.glasses. Broad emission bands and multicomponent fluorescence decay curves in Duran glasses indicate very strong Mn-Mn ion interactions and the presence of multiple Mn2+ sites, even at low Mn-levels. The EPR spectra show exchange narrowing with increasing Mn content in the Duran series, which is caused by a decrease in the Mn-Mn distances as edge sharing MnO6 octahedra are formed. The network structure of Mn-containing binary and ternary borate glasses is discussed on the basis of their infrared spectra. Addition of MnO to Duran glasses is found to cause the preferential transformation of [BO3](0) to [BO4](-) groups, and to a lesser extent of silicate Q(4) to Q(3) units. An increase of the relative population of homopolar B-O-B or Si-O-Si bonds, with the simultaneous decrease in the number of mixed B-O-Si bonds, is also observed, and this explains the visible phase separation of Duran glasses when MnO is added in excess of 4 mol%.

Zinc and manganese borates and borosilicates were prepared and investigated. Binary ZnO-B2O3 and MnO-B2O3 melts show similar stable phase separation below 50 mol% ZnO or MnO. Two layers were separated in the melts. The upper layer was nearly pure B2O3 and contained crystals. The lower layer was zinc or manganese borate with around 50 mol% ZnO or MnO. Melts of ternary systems with SiO2 were separated into SiO2 rich and zinc or manganese rich phases. The addition of Na2O decreases phase separation. Compositions with more than 50 mol% ZnO provided clear homogeneous glass samples. Mn2+ was substituted for Zn2+ in glasses and crystals, with a coordination number from 6 to 4, and a variation of Me photoluminescence from orange-red to yellow-green depending on local structure. A drastic change of luminescence was detected when the glass was transformed to a glass ceramic by thermal treatment. Adding Eu2O3 or Tb2O3 to zinc borates provides strong orange-red (Eu3+) or green (Tb3+) luminescence. In phase separated samples, Mn2+, Eu3+ and Tb3+ were only accumulated in the zinc borate and not in the B2O3 phase. The large Eu3+ and Tb" ions could not substitute for Zn2+ in the crystal phases.

We present a plasma mirror configuration that improves the temporal pulse contrast of femtosecond terawatt laser pulses by a factor of thousand using a single antireflection coated glass target. The device provides ultra-high contrast for experiments with a maximum repetition rate of 10 Hz. A third-order cross-correlator has been used to measure the temporal pulse contrast for several different plasma mirror targets. It is shown that the ASE can be suppressed to a level of 10−11. A comparison between a triggered and an untriggered plasma mirror reveals differences in the intensity distribution of the focused beam. The triggered plasma mirror produces a slightly larger focus due to the expansion of the triggered plasma mirror at −3 ps before the main pulse. We propose a cost-effective AR-coated and a blank glass target to reduce the costs of the consumable target material. High-harmonic radiation on solid surfaces has been generated with different plasma mirror targets to demonstrate the high laser contrast.

Photoluminescence (PL) behaviour of four different glasses and glass ceramics with the following compositions (in mol%) was investigated: 40ZnO-10Al(2)O(3)-50SiO(2) (ZAS) with Zn(2)SiO(4) (willemite) and ZnAl(2)O(4) (gahnite) crystals, 30ZnO-10BaO-10Na(2)O-50SiO(2) (ZBNS) with BaZn(2)Si(2)O(7) crystals, 40BaO-20TiO(2)-40SiO(2) (BTS) with isochemical Ba(2)TiSi(2)O(8) (fresnoite) crystals and 35CaF(2)-23Al(2)O(3)-2P(2)O(5)-40SiO(2) (CAS) with CaF(2) crystals. Blue luminescence of four-fold coordinated Zn(2+) and five-fold coordinated Ti(4+) arising from excitation at similar to 250 nm was more efficient in crystals than in glasses. Mn(2+) ions give a weak orange-red emission in ZAS glasses due to predominant six-fold coordination and a strong green luminescence in Zn(2)SiO(4) and ZnAl(2)O(4) crystals due to four-fold coordination. Mn(2+) can substitute for Zn(2+) ions in the crystal phases. Rare earth (RE) ions cannot substitute for smaller Zn(2+) ions, but can substitute for large Ba(2+) and Ca(2+) ions in the crystal phases BaZn(2)Si(2)O(7), Ba(2)TiSi(2)O(8) and CaF(2). Static and time resolved photoluminescence behaviour of Tb(3+), Eu(3+), and Er(3+) in doped glasses and glass ceramics were investigated. Much higher PL efficiency and shorter decay times were found in the glass ceramic (fresnoite) than in glass samples of the isochemical system 40BaO-20TiO(2)-40SiO(2), blue for Ti(4+), red for Eu(3+), and green for Tb(3+), with energy transfer from Ti(4+) to Eu(3+), and to Tb(3+). Oxyfluoride (CAS) samples doped with Eu(3+), Tb(3+), or Er(3+) had only CaF(2) as a crystal phase. Only in the case of Er(3+) did the spectra of the crystalline CaF(2) phase dominate with efficient green and red emission and longer decay times by down- and upconversion.

Electron paramagnetic resonance (EPR) and fluorescence spectroscopy are sensitive and selective methods for probing coordination and bonding of Mn2+ ions in glasses. Both methods provide additional information on Mn–Mn ion interactions and cluster formation. Mn2+ was found to be tetrahedrally coordinated in boro-silicate glasses of high optical basicity, and octahedrally coordinated in low alkaline boro-silicate glasses (duran-type) as in fluoride-phosphate glasses. Broad emission bands and multicomponent fluorescence decay curves in duran glasses indicate very strong Mn–Mn ion interactions and the presence of multiple Mn2+ sites. Site distribution is more homogenous in metaphosphate glasses, though concentration quenching is apparent at high Mn-levels. As the Mn-content increases the EPR spectra show exchange narrowing due to a decrease in the Mn–Mn distances in the duran series, but show extreme linewidth broadening due to increased cluster sizes at constant Mn–Mn distances for metaphosphate glasses. For the fluoride-phosphate and boro-silicate systems investigated, fluorescence lifetimes are found to decrease as the wavelength of the emission maximum increases and with increasing g-values of the sextet at g=2. For octahedral coordination of Mn2+ ions the EPR hyperfine splitting constant decreases linearly with increasing optical basicity, as a result of an increasing covalent character of the Mn2+–ligand bond.

Glass and its properties are subject to a variety of changes for many applications. In the last years systematic studies and developments were carried out in the fields of active Nd3+ (f3), Er3+ (f11), and Yb3+ (f13) laser and amplifier glasses. Fluoride and oxide glasses with high intrinsic UV transmission were doped with luminescent species of various electronic configurations, s2: As3+Sb3+Sn2+Pb2+; d0: Ti4+Nb5+Mo6+Ta5+W6+; d10: Zn2+Ag+Cu+; d5: Mn2+; fn: Ce3+(f1), Pr3+ (f2), Sm3+ (f5), Eu3+ (f6), Eu2+ (f7), Tb3+ (f8), Dy3+ (f9), Ho3+ (f10), Er3+ (f11) and Tm3+ (f12). Static and time resolved photoluminescence behavior in the ultraviolet and visible range was investigated depending on glass matrices and concentration of luminescent species. Also the luminescence of Bi-doped glasses was studied, where the kind of the luminescent Bi-species is still unknown. Some glasses were transformed in glass ceramics by thermal treatment. A change of coordination from 6 to 4 was detected for Zn2+ and Mn2+ in the ZnO-Al2O3-SiO2 system. Luminescence intensity can be increased or decreased depending on various conditions.