Intense red upconversion emission of Yb/Tm/Ho triply-doped tellurite glasses

By conventional melting and quenching methods, 3Yb(2)O(3)-0.2Tm(2)O(3)-xHo(2)O(3) (wt%, x = 0.2 similar to 1.2) was doped into an easily fiberized tellurite glass with composition of 78TeO(2)-10ZnO-12Na(2)O (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: F-5(5) -> I-5(8)) and were responsible for the absence of the usually observed 484 nm emission (Blue, Tm: (1)G(4) -> H-3(6)). 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: S-5(2) -> I-5(8)). 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. (C) 2012 Optical Society of Americ