Jianbei Qiu

Upconversion luminescence of Er3+ in transparent SiO2—PbF2—ErF3 glass ceramics

Oxyfluoride glasses with the composition 50SiO2 · 50PbF2 · xErF3 (x=4 and 5) by molar ratio were developed. Transparent glass ceramics were obtained by heat-treating the 50SiO2 · 50PbF2 · xErF3 glasses at the first crystallization temperatures. X-ray diffraction analysis of the transparent glass ceramics revealed that fluorite type β-PbF2:Er3+ solid solution regions of about 13.0 nm in diameter are precipitated in the glass matrix. The formation of this β-PbF2:Er3+ solid solution was also supported by Eu3+ fluorescence spectra which were measured on specimens in which Eu substituted for Er. Under 800 nm laser excitation, the Er3+ upconversion luminescence of 50SiO2 · 50PbF2 · xErF3 glasses was barely detectable, but the 50SiO2 · 50PbF2 · xErF3 glass ceramics gave Er3+ upconversion luminescence at a very high efficiency. The reason for the highly efficient Er3+ upconversion luminescence in the 50SiO2 · 50PbF2 · xErF3 glass ceramics can be explained in terms of the very small multiphonon relaxation rates that are anticipated from consideration of the Eu3+ emission spectra.

Sensitized Ho3+ up-conversion luminescence in Nd3+–Yb3+–Ho3+ co-doped ZrF4-based glass

As previously reported, a selectively strong green emission due to the Ho3+: (5F4, 5S2)→5I8 transitions is observed in Nd3+–Ho3+ co-doped ZrF4-based fluoride glasses under 800 nm excitation. As an attempt to more enhance Ho3+ up-conversion luminescences in the Nd3+–Ho3+ co-doped ZrF4-based glasses, Yb3+ ions were added to the glasses. As a result it was found that, in 800 nm excitation of 60ZrF4⋅30BaF2⋅(8−x)LaF3⋅1NdF3⋅xYbF3⋅1HoF3 glasses (x=0 to 7), sensitized up-conversion luminescences are observed at around 490 nm (blue), 545 nm (green), and 650 nm (red), which correspond to the Ho3+: 5F3→5I8, (5F4, 5S2)→5I8, and 5F5→5I8 transitions, respectively. The intensities of the green and red emissions in a 3 mol % YbF3-containing glass were about 50 times stronger than those in no YbF3-containing glass. This is based on sensitization due to Yb3+ ions. In particular, the green emission is extremely strong so that the Nd3+–Yb3+ –Ho3+ co-doped ZrF4-based glasses have a high possibility of realizing a green up-con...

New oxyfluorotellurite glass: thermal analysis and structural analysis by means of Raman scattering

The TeO2–BaO–BaF2–La2O3–LaF3 oxyfluorotellurite glass system is newly developed. Differential thermal analysis (DTA) and structural analysis by Raman scattering spectra are reported on the 70TeO2·(20−x)BaO·xBaF2·(10−y) La2O3·yLaF3 composition (x=0, 5, 10, 15, 20; y=0, 5, 10). The DTA results indicated that an increase of fluoride content in the glasses decreases the glass-transition temperature (Tg) and increases the crystallization-onset temperature (Tc). As a result, the 70TeO2·20BaF2·10LaF3 glass showed a large Hrubýs parameter, possessing excellent thermal stability. Changes in glass-network structure with fluoride content are discussed based on the Raman scattering spectra of glasses. The glass-network structures in the 70TeO2·(20−x)BaO·xBaF2·(10−y) La2O3·yLaF3 glasses are basically composed of both Te(O, F)4 and Te(O, F)3 units, but the Te(O, F)4/Te(O, F)3 ratio in the glass becomes higher with increasing fluoride content. This may be considered one of the reasons why the 70TeO2·20BaF2·10LaF3 glass exhibits excellent thermal stability. This improved thermal property gives a new possibility of the present oxyfluorotellurite glass for optical applications such as rare-earth-doped fiber fabrication.

Blue up-conversion luminescence and energy transfer process in Nd3+-Yb3+-Tm3+ co-doped ZrF4-based glasses

Up-conversion luminescence properties and energy transfer processes in Nd3+, Yb3+, and Tm3+ co-doped ZrF4-based fluoride glasses have been studied under 800 nm light excitation. Blue up-converted emission around 478 nm which can be assigned to the Tm3+: 1G4→3H6 transition, was strongly observed. Up-conversion luminescence intensity exhibited an YbF3-concentration dependence. Among Nd3+, Yb3+, and Tm3+, both Nd3+ and Tm3+ have ground state absorption bands due to the (2H9/2, 4F5/2) ←4I9/2 and 3F4←3H6 transitions, respectively, which can be directly pumped by 800 nm light. However, no emissions were observed in Tm3+ singly doped and Tm3+-Yb3+ doubly doped glasses under 800 nm excitation. Therefore, a possible up-conversion mechanism may be proposed as follows: Energy transfer firstly occurs from Nd3+ to Yb3+ when Nd3+ is excited by 800 nm light, then the energy is transferred from Yb3+ to Tm3+ which is on the excited state and, finally, blue up-conversion emission of Tm3+ is observed through the Tm3+: 1G4→3...

Selectively strong green up-conversion luminescence in co-doped -based fluoride glasses under 800 nm excitation

Blue, green and red up-conversion luminescences at around 490, 545 and 650 nm, which result from the , and transitions, respectively, were observed in co-doped -based fluoride glasses under 800 nm excitation. Among these up-conversion luminescences, the green emission was extremely strong and the blue and red emission intensities were very weak. Selectively strong green up-conversion luminescences of these glasses indicate a high possibility for realizing a green up-conversion laser. Up-conversion processes for the blue, green and red emissions are two-photon processes assisted by energy transfer. It is proposed that the up-conversion mechanism for the blue and green emissions is different from that for the red emission. The respective mechanisms are discussed.

Long-lasting phosphorescence in Sn2+–Cu2+ codoped silicate glass and its high-pressure treatment effect

Long-lasting phosphorescence was observed at 510 nm in a Sn2+–Cu2+ codoped Na2O–CaO–SiO2 glass at room temperature under UV illumination of 254 nm. When the glass was compressed under 3, 6, and 9 GPa, the phosphorescence shifted to 465 nm and its decay rate became shorter. The optical absorption spectra of the samples changed after compression, showing that the cupric ions were reduced to the cuprous ions. The high-pressure treatment also resulted in a lower-energy shift in the absorption edge. It was suggested that Sn2+ ions act as hole trapping centers, while oxygen vacancies surrounding by Ca2+ ions as well as active sites in the glass matrix, i.e., as electron trapping centers.

FARADAY EFFECT OF GAS3/2-GES2-LAS3/2-BASED GLASSES CONTAINING VARIOUS RARE-EARTH IONS

Sulfide glasses of 50GaS3/2⋅20GeS2⋅20LaS3/2⋅10LnSn/2 (Ln=rare earth ions, n=2 for Eu and 3 for other ions) compositions have been prepared. The wavelength dispersions in the Faraday effect of the glasses have been examined. Glasses containing LaS3/2 and YS3/2 have positive Verdet constants in the wavelength region from 550 to 850 nm, and the magnitude of the Verdet constants decreases with increasing wavelength. On the other hand, the Verdet constants of glasses containing Eu2+ and Ce3+ are negative, and the absolute magnitude of the Verdet constants decreases with increasing wavelength. The effective transition wavelengths of glasses containing various paramagnetic rare‐earth ions have been calculated based on the Van Vleck and Hebb theory. Factors determining the Verdet constants of these glasses are discussed.

Structural study of GeS2 glasses permanently densified under high pressures up to 9 GPa

Abstract The structures of GeS 2 glasses permanently densified under 1.5, 3.0, 4.5, 6.0 and 9.0 GPa have been investigated by means of Ge–K EXAFS, Ge–K and S–K XANES, X-ray radial distribution, Raman scattering and optical absorption. The experimental results have been analyzed based on the structures of α (high-temperature form)-, β (low-temperature form)- and II (high-pressure form)-GeS 2 crystals. The densities of permanently densified glasses increased monotonously with increasing applied-pressure until 6.0 GPa and then reached a constant value in a pressure range from 6.0 to 9.0 GPa. With increasing densification the structure of GeS 2 glass, which is an intermediate between the structures of α-GeS 2 and β-GeS 2 at atmospheric pressure, was progressively converted into a II-GeS 2 -like structure with no large hollows. The red shift of optical absorption edge in the visible region that results from densification exhibited the same pressure dependence as that observed for density.

Peculiar high-pressure behavior in permanent densification of fluorozirconate glass

Abstract A 60ZrF 4 ·30BaF 2 ·10EuF 3 glass was densified under 1.5, 3.0, 4.5, 6.0, and 9.0 GPa at 250°C using a 6–8-type multi-anvil high-pressure apparatus. The densities of permanently densified glasses exhibit a maximum value at the 3.0 GPa treatment and then a marked decrease with increasing pressure. Such a peculiar permanent densification behavior, being reported for the first time to the best of our knowledge, is discussed based on the F − coordination environments around Zr 4+ , Eu 3+ , and Ba 2+ . This behavior may be attributed to a spontaneous structure-relaxation.

Upconversion of glass ceramics and its application

Oxyfluoride glasses of the compositions of 50SiO2•50PbF2•(5 - x)GdF3•xErF3 and 50SiO2•50PbF2•(5 - y)GdF3•0.1NdF3•yYbF3•0.1(Tb, Ho, Er or Tm)F3 in molar ratio (x =0.3 - 5 and y = 0 - 5) were developed. The oxyfluoride glasses were heat-treated at their first crystallization temperatures. Consequently, the crystals of -PbF2:(trivalent rare-earth ions) solid solutions uniformly precipitated in the scales of 15 20 nm in diameter in silicate glass matrices. These glass-ceramics were transparent to the naked eye. The glass-ceramics gave highly efficient upconversion luminescence based on the Tb3+, Ho3+, Er3+ or Tm3+ ion under 800 and/or 980 nm light excitation. These oxyfluoride glasses can be locally changed to glass-ceramics in the forms of dots, lines, letters, planes, etc. by irradiation of various lasers. The forms written by laser irradiation can be easily read from upconversion luminescence generated by the 800 and/or 980 nm laser illumination. Thus, the present oxyfluoride glasses can be applied to an optical memory device for specific information. Plates, fibers, thin films and coating-films in which the glass-powders are embedded in inorganic and/or organic polymers are considered as the shapes of oxyfluoride glasses that can be utilized as the device.