Blue cooperative upconversion in Yb3+-doped glass ceramic containing LiYF4 nanocrystals

A transparent Yb3+ doped oxyfluoride glass ceramic containing LiYF4 nanocrystals was developed. Under 940 nm laser diode pumping, blue luminescence emission around 480 nm through cooperative upconversion from pairs of Yb3+ ions was obtained. Cooperative luminescence emission enhanced due to LiYF4 nanocrystals precipitated in the glass matrix was observed. The cooperative luminescence mechanisms were proposed based on spectral, kinetic and pump power dependence analyses. Moreover, Stark level splitting and near-infrared radiation shifting, owing to the change of Yb3+ ions from a glass site to a crystal site, were also discovered.