Upconversion luminescence in Er3+-doped germanate-oxyfluoride and tellurium-germanate-oxyfluoride transparent glass-ceramics

Upconversion luminescence has been studied for Er3+ in a germanate-oxyfluoride and a tellurium-germanate-oxyfluoride transparent glass-ceramic using 800 nm excitation. Significantly increased upconversion luminescence was observed from transparent glass-ceramics compared with that from their corresponding as-prepared glasses. In addition to a strong green emission centered at 545 nm from S-4(3/2) state and a weaker red emission centered at 662 nm from F-4(9/2) state generally seen from Er3+-doped glasses, a violet emission centered at 410 nm from H-2(9/2) state and a near-ultra-violet emission centered at 379 nm from (4)G(11/2) state were also observed from transparent glassceramics. The upconversion luminescence of Er3+ ions in transparent glass-ceramics revealed sharp Stark-splitting peaks generally seen in a crystal host. The increased upconversion efficiency is attributed to the decreased effective phonon energy and the increased energy transfer between excited ions when Er 31 ions were incorporated into the precipitated beta-PbF2 nanocrystals. (C) 2006 Elsevier B.V. All rights reserved.