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 4S3/2 state and a weaker red emission centered at 662 nm from 4F9/2 state generally seen from Er3+-doped glasses, a violet emission centered at 410 nm from 2H9/2 state and a near-ultra-violet emission centered at 379 nm from 4G11/2 state were also observed from transparent glass-ceramics. 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 Er3+ ions were incorporated into the precipitated β-PbF2 nanocrystals.