Changes in glass structure and crystallization behaviour from oxyfluoride silicate glass to oxyfluoride germanate glass were studied by modifying the ratio of Si/Ge in oxyfluoride germanosilicate glass ceramics, and transparent glass ceramic with low light scattering and efficient mid-infrared emissions were obtained. The NaYF4 nanocrystals crystallization ability of oxyfluoride glass was decreased with the increase in Ge content, which can be attributed to the weakened oxide and fluoride phase separation in GeO2-rich glass. Upconversion and downconversion emission spectra together with Ho3+: 5I6 energy level fluorescent decay curves have been discussed for SiO2-rich glass ceramics and GeO2-rich glass ceramics, in which the fluoride crystallization induced the decrease of multi-phonon non-radiative decay rates plays the main role in the energy transfer processes. The influence of Si/Ge ratio on 2 mu m and 3 mu m fluorescent emissions in glasses and glass ceramics, and its link with glass network structural changes were discussed. The optimized Yb/Ho codoped oxyfluoride germanosilicate glass ceramic with low light scattering, high peak emission cross section(11.18 x 10-21cm2) and maximum gain coefficient (1.387 cm-1) at 2888 nm provides a potential application in the development of new 3 mu m laser devices based on transparent oxyfluoride glass ceramic materials.

Rare earth doped luminescence glasses have been noteworthy recently in the fields of near-middle-infrared applications. In this work, serious Er3+ doped new kind of germanosilicate-zinc glasses have been investigated aiming to obtain efficient infrared and mid-infrared luminescence performance. The drastically reduced OH- content in present host support the enhanced 2.7 and 1.5 mu m emissions corresponding to the I-4(11/2 )-> I-4(13/2) and I-4(13/2) -> I-4(15/2) transitions owing to the decreased energy loss between OH- and active ions. Meanwhile, the energy transfer mechanism has been discussed based on both the infrared and visible spectra together with the measured decay curves. Hence, the large absorption and emission cross-sections indicate that this kind of germanosilicate-zinc glasses may provide high gain as a good medium for efficient infrared laser system.

Researching broadband amplification materials and modulating energy transfer processes between two active ions have attracted immense attention for photoluminescence applications in recent years. In this work, transition metal (Cr) and rare earth (Er) ions codoped glasses and glass ceramics with ten nanometer length scale beta-Zn2SiO4 crystals have been successfully prepared. The analysis of valence state change and surroundings of Cr ions proves two points: 1) Cr3+ ions always stay in amorphous surroundings, 2) a part of Cr3+ ions change to Cr4+ occupied in the nanocrystal phase. To the best of our knowledge, it is demonstrated for the first time that an active ion (Cr3+) does not produce the radiative processes by emitting photons, while it can store pumping energy and transfer to neighboring active ions (RE: Er3+ ions here) for infrared emission. Four times enhanced infrared intensity of 1530 nm emission and super-ultrabroadband emisison in the region of 1100-1700 nm have been obtained finally. Meanwhile, an approach in nanometer length scale to control ET processes between two simultaneous active ions has been proposed for futher studies on photoluminescence applications. (C) 2019 Elsevier B.V. All rights reserved.

Bi can experience chemical-state evolution by structural engineering of glass network, which is favorable for the efficient manipulation of final luminous property, as well as the extensive potential in new type fiber lasers and optical amplifiers. In this work, the typical structure of glass is transformed and optimized by designing and tuning both the glass network formers and modifiers. It is fist time to demonstrate that the mixed-structure effect produced by the formation of the hybrid structure (SiO2-GeO2) is conducive to the Bi-related near-infrared (NIR) emission. In addition, the dispersion of Bi-related NIR emission centers is further tailored by the AlO5 hexahedra in this multicomponent glass, which is claimed by both NMR and emission spectra. Furthermore, a suitable reduction atmosphere is designed appropriately to promote the NIR luminescence to a larger extent. This work is expected to be helpful for improving the performance of existing Bi-doped glass and fibers. Our results indicate that the tuned multicomponent germanosilicate glasses with mixed structure and optimal reduction effect can be promising material as high performance photonic glasses.

Diode-pumped solid-state 2 mu m lasers have seen rapid development for their efficient operation, compact size, and stable performance. In this work, doped germanosilicate (SiO2-GeO2-Ga2O3-Lu2O3) glasses with varying Tm3+/Ho3+ concentrations exhibiting excellent physical and optical characteristics were successfully prepared. Thermal and structural properties were analyzed by the measured DSC and Raman spectra. An evident efficient wide absorption band near 770-830 nm demonstrated the feasible energy transfer between Tm3+:F- 3(4) -> H-3(6) and Ho3+: I-5(7) -> I-5(8) transitions. Meanwhile, combining with Judd-Ofelt theory, super predicted spontaneous emission probabilities were obtained, which are beneficial to obtain fine laser action for solid-state lasers. This is a first study to demonstrate that a tunable fluorescence peak (1.8-2.05 mu m) can be obtained by modulating the combined effects between two luminous activation centers. Therefore, the results indicate a promising rare-earth doped glass host for solid-state 2 mu m lasers.