Infrared to visible upconversion of Er3+ and Er3+/Yb3+ codoped lead-niobium-germanate glasses

Infrared-to-visible upconversion processes have been investigated in Er3+-doped and Er3+/Yb3+, codoped lead-niobium-germanate glass (55GeO(2)-25PbO-20Nb(2)O(5)) with a fixed 0.5 mol%, Er3+ concentration and different Yb3+ concentrations ranging from 0 to 2 mol%. Visible emissions at 526, 547, and 660 nm corresponding to the H-2(11/2) --> I-4(15/2), S-4(3/2) --> I-4(15/2), and F-4(9/2) --> I-4(15/2) transitions were observed under continuous wave excitation at 978 nm. The quadratic pump power dependence of these emissions indicates a two photon upconversion process. An enhancement of the visible upconversion fluorescence in Er3+/Yb3+ codoped samples is confirmed due to efficient energy transfer from Yb3+ to Er3+ ions. (C) 2003 Elsevier B.V. All rights reserved.