Upconversion fluorescence spectroscopy of Er 3+-doped lead oxyfluoride germanate glass

Abstract

The upconversion fluorescence properties of Er 3+-doped lead oxyfluoride germanate glass excited at 975 nm are investigated experimentally. Intense green and red signals centered at 529, 551, and 657 nm, corresponding to the 2H 11/2→ 4I 15/2, 4S 3/2→ 4I 15/2, and 4F 9/2→ 4I 15/2 transitions of Er 3+, respectively, were simultaneously observed at room temperature. Raman spectrum indicates the important role of fluoride ions in the formation of glass network. The dependence of upconversion intensities on excitation power presents the two-photon absorption processes for the three emission bands. The possible upconversion mechanisms are discussed based on the energy-matching conditions and the quadratic dependence on excitation power. The intense upconversion fluorescence of Er 3+-doped lead oxyfluoride germanate glass may be a potentially useful material for developing upconversion fiber optical devices.