The role of a three-ion energy transfer process in the violet fluorescence in highly doped Er3+:ZB(L)AN glasses

The violet (∼400–410-nm) fluorescence in Er3+:ZB(L)AN glasses has been previously attributed to transitions originating from the 2H9/2 and 2P3/2 levels. The study reported here found that, in high Er3+ concentrations and with 800-nm excitation, a significant source of violet fluorescence around 407-nm was due to the previously unreported 4G9/2 → 4I9/2 transition. The study also established that, under these conditions, a three-ion energy transfer process originating in the 4I9/2 level is responsible for populating of the fluorescing 4G9/2 level.