Intense red upconversion emission of Yb/Tm/Ho triply-doped tellurite glasses.
By conventional melting and quenching methods, 3Yb2O3-0.2Tm2O3-xHo2O3 (wt%, x=0.2~1.2) was doped into an easily fiberized tellurite glass with composition of 78TeO2-10ZnO-12Na2O (mol%) to form YTH-TZN78 glasses. Under 976 nm excitation, the direct sensitizing effect of Yb ions (Yb→Ho) and indirect sensitizing and self-depopulating effects of Tm ions (Yb→Tm→Ho) were found to present intense red upconversion emission at 657 nm (Red, Ho:5F5→5I8) and were responsible for the absence of the usually observed 484 nm emission (Blue, Tm:1G4→3H36). Regardless of the dopant concentration of Ho ions, the intensity of the red emission at 657 nm (Red, Ho:5F5→5I8) is about three times stronger than that of the green one at 543 nm (Green, Ho:5S2→5I8). For this certain red emission at 657 nm, 0.4 wt% Ho2O3-doped YTH-TZN78 glass was found to present the highest emission intensity and is therefore determined as a promising active tellurite glass for red fiber laser development.
Gold nanoparticles assisted structural and optical modifications of samarium doped sodium-lithium tellurite glass
Modifying the physical and the optical properties of rare earth doped tellurite glasses by embedding metallic nanoparticles (NPs) with controlled size and optimized concentration is ever-demanding in solid state lasing materials. Thus, the influences of gold (Au) NPs concentration on the structural and the optical enhancements were examined. Two series of samarium (Sm3+) doped sodium tellurite glasses, with and without Au NPs, which had compositions of (80-x)TeO2 + 10Li2O + 10Na2O + xSm2O3 (where 0.0 ≤ x ≤ 3.0 mol%) and 79TeO2 + 10Li2O + 10Na2O + 1Sm2O3 + yAuCl3 (where 0.03 ≤ y ≤ 0.15 mol% in excess), respectively, were prepared using melt-quenching technique. Subsequent annealing at 300°C for 3 hours was performed to control the growth of NPs. Structural and optical characterizations were determined using XRD, TEM, UV-Vis-NIR, FTIR, and PL measurements. XRD pattern confirmed the amorphous nature of the prepared glasses, whereas the TEM image manifested the growth of spherical NPs with mean size ~18 nm. Meanwhile, FTIR spectra displayed four broad absorption bands, which were assigned to TeO4 and TeO3 tetragonal pyramids, stretching vibration of hydroxyl group, and stretching vibration of strong metal bonding. In addition, the UV-Vis spectra exhibited six peaks that were centered at 471, 948, 1085, 1246, 1395 and 1494 nm, corresponding to the transition from ground state to different excited states of Sm3+ ion. Besides, significant enhancement in the absorption was observed for 0.09 mol% of Au NPs, while the Urbach energy showed an increase from 0.2374 to 0.2588 eV with the increase of NPs concentration. On top of that, the PL spectra displayed four enhanced peaks that were centered at 573, 613, 658 and 718 nm, which had been associated with the transition from the excited states to the ground state of Sm3+ ion. The enhancement was attributed to the surface plasmon resonance (SPR) effect and the strong local field of NPs positioned in the proximity of Sm3+ ion. Modifications in the physical, structural, and optical properties that originated from the alteration of glass network structure in the presence of Au NPs were analyzed and discussed. Furthermore, the mechanism of enhancement was comprehended and compared. The excellent features of the retrieved results suggest that these glasses may be nominated as potential candidates for solid state lasers, displays, and amplifiers.
SR topography of plastically deformed Fe-Si bicrystals - observation in situ and post mortem
SR reflection topography was applied to study the interaction of slip dislocations with the grain boundaries in Fe-4at%Si bicrystals deformed by compression. Three experimental settings with either a white or monochromatic beam were used and the corresponding orientation contrast analysed. Dislocation transmission through the grain boundary was observed in bicrystals with favourable geometry of the slip systems.