Violet and near-ultraviolet upconversion luminescence in La3Ga5.5Ta0.5O14 codoped with Er3+ and Yb3+

Violet (410 nm, 2H9/2→4I15/2) and near-ultraviolet (380 nm, 4G11/2→4I15/2) upconversion luminescence, were obtained for the first time in Er:Yb:La3Ga5.5Ta0.5O14 ceramic sample, synthesized by solid-state reaction, by pumping at 973 nm. Yb3+-Er3+ energy transfer processes accounting for population of the emitting levels are discussed. The lifetime of the emitting level 2H9/2, responsible for violet luminescence, was measured and its quantum efficiency was estimated.