Growth and spectroscopic investigations of Yb,Ho: YAP and Yb,Ho,Pr:YAP laser crystals

Yb,Ho:YAP and Yb,Ho,Pr:YAP laser crystals with high optical quality are successfully grown using the Czochralski method. The absorption coefficient and band width of the two crystals at 970 nm are increased because of the doping of Yb3+ sensitizer. The three strongest fluorescence peaks of the two crystals are located at approximately 2844, 2853, and 2912 nm, which correspond to the 5I6→5I7 level transitions of Ho3+ ions. Lifetime measurements indicate that the deactivator Pr3+ ions can efficiently decrease the lifetime of the lower level 5I7 from 8.848 ms to 1.258 ms. Energy-transfer mechanisms are also studied and analyzed, and up-conversion luminescence spectra provide the further evidence that Pr3+ ions can efficiently depopulate Ho3+ ions at the 5I7 level. All these results show that Yb,Ho,Pr:YAP crystal may be a promising laser medium for realizing 2.8-3.1 μm lasers pumped using a 970 nm laser diode.