The sensitization effects of Nd3+ and Tm3+ to obtain enhanced 2.9 mu m emission of Dy3+ in CaYAlO4 crystals

Single crystals of Dy3+/Tm3+ and Dy3+/Nd3+ co-doped CaYAlO4 were successfully grown, and could emit enhanced 2.9 mu m mid-infrared fluorescence emission. The sensitization effects of Tm3+ and Nd3+ on the spectroscopic properties and energy transfer mechanisms between the sensitized ions (Tm3+ or Nd3+) and Dy3+ were studied. In comparison with the Dy3+ singly-doped CaYAlO4 crystal, the co-doped crystals have stronger absorption bands at around 800 nm. Under excitation by a commercial AlGaAs laser diode, the two co-doped crystals exhibit superior mid-infrared emission, as expected. Moreover, the efficiencies of the energy transfer from Tm3+ to Dy3+ and Nd3+ to Dy3+ in the co-doped crystals were 87.9% and 78.5%, respectively. Besides, according to the phonon-assisted energy transfer theory, the energy transfer microscopic parameters between sensitized ions (Tm3+ or Nd3+) and Dy3+ were theoretically calculated. The results indicate that Tm3+ and Nd3+ ions could be used as effective sensitizers of Dy3+, and the Dy3+/Tm3+:CaYAlO4 and Dy3+/Nd3+:CaYAlO4 crystals could be used as promising media for similar to 2.9 mu m laser operation under excitation by an AlGaAs laser diode.