Near-IR Luminescence of Rare-Earth Ions (Er3+, Pr3+, Ho3+, Tm3+) in Titanate-Germanate Glasses under Excitation of Yb3+

Inorganic glasses co-doped with rare-earth ions have a key potential application value in the field of optical communications. In this paper, we have fabricated and then characterized multicomponent TiO2-modified germanate glasses co-doped with Yb3+/Ln(3+) (Ln = Pr, Er, Tm, Ho) with excellent spectroscopic properties. Glass systems were directly excited at 980 nm (the F-2(7/2) -> F-2(5/2) transition of Yb3+). We demonstrated that the introduction of TiO2 is a promising option to significantly enhance the main near-infrared luminescence bands located at the optical telecommunication window at 1.3 mu m (Pr3+: (1)G(4) -> H-3(5)), 1.5 mu m (Er3+: I-4(13/2) -> I-4(15/2)), 1.8 mu m (Tm3+: F-3(4) -> H-3(6)) and 2.0 mu m (Ho3+: I-5(7) -> I-7(8)). Based on the lifetime values, the energy transfer efficiencies (eta(ET)) were estimated. The values of eta(ET) are changed from 31% for Yb3+/Ho3+ glass to nearly 53% for Yb3+/Pr3+ glass. The investigations show that obtained titanate-germanate glass is an interesting type of special glasses integrating luminescence properties and spectroscopic parameters, which may be a promising candidate for application in laser sources emitting radiation and broadband tunable amplifiers operating in the near-infrared range.