title: Analysis of upconversion luminescence in germanate glass and optical fiber codoped with Yb3+/Tb3+.
abstract: In this paper, upconversion (UC) luminescence processes in a GeO2-Ga2O3-BaO glass system codoped with 0.7Yb2O3/(0.07-0.7)Tb2O3(mol.%) and double-clad optical fiber codoped with 0.7Yb2O3/0.7Tb2O3(mol.%) were investigated. The highest emission intensity (energy transfer efficiency equals 12.92%) was obtained for 0.7Yb2O3/0.7Tb2O3codoped glass. Comparative analysis showed significant differences in the shape of luminescence of fabricated germanate glass and optical fiber. Due to dominant transition from D45 sublevel the main green UC peak (Tb3+:  D45→F57) of fabricated double-clad optical fiber is shifted by 4 nm toward longer wavelengths.
authors.forename: M
authors.initials: M
authors.lastname: Kochanowicz
authors.forename: J
authors.initials: J
authors.lastname: Zmojda
authors.forename: P
authors.initials: P
authors.lastname: Miluski
authors.forename: M
authors.initials: M
authors.lastname: Sitarz
authors.forename: J
authors.initials: J
authors.lastname: Pisarska
authors.forename: W A
authors.initials: WA
authors.lastname: Pisarski
authors.forename: D
authors.initials: D
authors.lastname: Dorosz