Ho3+:: (5S2, 5F4) → 5I5 transition in fluoride glasses

We propose that Ho3+ and Ho3+/Yb3+-doped fluoride glasses are a good candidate material for fiber amplifiers operating at 1340-1400 nm band. Upconversion excitation in the wavelengths of 880-920 and 970-990 nm is achieved for Ho3+-single-doped glasses, while wavelength region of 910-1000 nm for Ho3+/Yb3+-codoped glasses. Ho3- concentration is preferably less than 0.5 mol% to avoid lifetime decrease of (S-5(2), F-5(4)) manifold. Yb3+ codoping enhances the upconversion excitation efficiency, however as Yb3+ concentration increases, back energy transfer from holmium to ytterbium slightly diminishes the fluorescing level lifetime. Some transition-metal ions and rare-earths ions doped in the clad part of a fluoride fiber waveguide, for example, may quench unwanted amplified spontaneous emissions at similar to540 nm and similar to750 nm. (C) 2002 Elsevier Science B.V. All rights reserved.