Infrared to visible up-conversion in thulium and holmium doped lutetium aluminum garnet

We report on the up-converted emissions at 367, 458 and 483 nm in thulium doped lutetium aluminum garnet (LuAG) under infrared excitation in the range of 730–800 nm. We also observe blue and strong green emission in thulium and holmium codoped LuAG with near infrared excitation. Excitation spectra, power dependence, temporal behavior and temperature dependence of up-converted emissions were measured to explain the up-conversion mechanisms. Several cross-relaxation mechanisms and excited state absorption are found to be responsible for the observed up-conversion processes.