Yellow-to-blue frequency upconversion in Pr3+-doped aluminium fluoride glasses

Rare-earth-doped fluoride glasses are attractive materials for photonics, s ince they combine a transmission region from ultraviolet to infrared and lo w vibrational cut-off energy. We report on the spectroscopic properties of aluminium fluorophosphate glasses doped with 0.1, 0.6, 1, 3 and 10 mol% Pr3 +. Yellow-to-blue upconversion was observed upon pulsed and continuous-wave (CW) excitation at 575 nm. The temporal evolution of the upconverted fluor escence is characterised by rise and decay times depending on Pr3+ concentr ation. The upconversion intensity has a quadratic dependence on incident pu mp power, indicating a two-step process. The upconversion emission is descr ibed in the framework of a two-ion energy transfer mechanism. Emission in t he second telecom window (1.3 mum) was measured upon excitation at 976 nm. (C) 2001 Elsevier Science B.V. All rights reserved.