Spectroscopic investigations of Ho3+/Er3+:CaYAlO4 and Eu3+/Er3+:CaYAlO4 crystals for 2.7 μm emission

Ho3+/Er3+:CaYAlO4 and Eu3+/Er3+:CaYAlO4 co-doped crystals were grown by Czochralski method. A detailed spectra analysis such as absorption spectra, up-conversion fluorescence, near-infrared and mid-infrared fluorescence spectra as well as luminescence decay curves was measured in order to optimize the deactivator for mid-infrared (2.7 μm) emission in Er3+: CaYAlO4 crystal. The influence of different deactivators on the spectra characteristics was studied. The energy transfer mechanisms, the related energy transfer coefficients and the stimulated emission cross-section were determined. Results show Ho3+ ion is the more appropriate deactivator than Eu3+ ion with which self-termination bottleneck effect was effectively suppressed. All imply that Ho3+ co-doping is beneficial for achieving 2.7 μm emission in Er3+:CaYAlO4 crystal.