Luminescence properties of Y2O3 single crystals doped with Pr3+ or Tm3+ and codoped with Yb3+, Tb3+ or Ho3+ ions

We have recorded fluorescence spectra and measured fluorescence lifetimes in yttria (Y2O3) single crystals doped with only Tm3+ or Pr3+ ions or codoped with Yb3+, Tb3+ or Ho3+ ions. The crystals were grown in the form of crystal fibers by using the laser heated pedestal growth (LHPG) technique. The codoped (Yb, Tm) and (Yb, Pr) crystals were studied for their potential as upconversion laser systems. Evidence is shown of cooperative and multi-step energy transfers giving rise to very efficient visible emissions after pulsed infrared excitation. As to the codoped (Tm, Ho) and (Tm, Tb) crystals, they are studied to examine the effect of the codopants on the infrared emission properties of the Tm3+ ions. Indeed, we found a very attractive fluorescence around the eye-safe wavelength of 1.55 mu m which corresponds to a H-3(4)-->F-3(4) transition of Tm3+. This transition occurs with a large enough stimulated emission cross section to be practical for laser application, and the Tb3+ or the Ho3+ ions are introduced to reduce the problem of bottlenecking due to a lower laser state lifetime longer than that of the upper state.