Green up-conversion in Yb super(3+) -Tb super(3+) and Yb super(3+) -Tm super(3+) -Tb super(3+) doped fluoro-germanate bulk glass and fibre

• Published in: Optical materials Vol. 33; no. 2; pp. 159 - 163
• Main Authors: Scarnera, V, Richards, B, Jha, A, Jose, G, Stacey, C
• Format: Journal Article
• Language: English
• Published: 01-12-2010
• Subjects: Bulk sampling; Excitation; Fibre; Glass; Lasers; Mesas; Optical materials; Terbium; Upconversion
• ISSN: 0925-3467
• DOI: 10.1016/j.optmat.2010.08.006

Yb super(3+)-Tb super(3+) and Yb super(3+)-Tm super(3+)-Tb super(3+) doped fluoro-germanate glass samples were fabricated in bulk and fibre form. Bright up-conversion has been obtained by exciting the samples with a 975 nm laser source, and the power dependence of the up-conversion intensities with respect to the excitation power has been characterised. Two mechanisms must be taken into account to explain the population of the super(5)D sub(4) level of the terbium ions in these experiments; namely multi excited state absorption (MESA) and cooperative up-conversion (CU). While in the Yb super(3+)-Tm super(3+)-Tb super(3+) samples both MESA and CU contribute simultaneously to the super(5)D sub(4):Tb super(3+) population, in the Yb super(3+)-Tb super(3+) case a pure CU mechanism is responsible for the super(5)D sub(4):Tb super(3+) population. In the fibre geometry, the re-absorption effect has been observed. The detrimental role of the re-absorption has been explained by characterising the up-conversion spectrum at different fibre lengths.