Sensitization and deactivation effects of Nd^3+on the Ho^3+ : 39 μm emission in a PbF_2 crystal

The use of Nd3+ codoping for sensitizing the Ho3+ ion and enhancing the ∼3.9 μm emission from Ho3+:I55→I65 was investigated in the PbF2 crystal for the first time, to the best of our knowledge. The ∼3.9 μm fluorescence emission properties and energy transfer mechanism of the as-grown crystals were investigated. The results show that the Nd3+ ion can act as a sensitizer to the Ho3+ ion, providing an efficient excitation channel, making the Ho3+/Nd3+:PbF2 crystal propitious to be pumped by commercialized InGaAs laser diodes (LDs). Moreover, an enhanced ∼3.9 μm emission was obtained in the Ho3+/Nd3+:PbF2 crystal due to the codoping of Nd3+ ions, leading to an efficient energy transfer from a lower laser level of Ho3+:I65 to Nd3+:I15/24, while having little influence on the higher laser level of Ho3+:I55. These advantageous spectroscopic characteristics indicate that the Ho3+/Nd3+:PbF2 crystal might have potential application in ∼3.9 μm mid-infrared lasers under a conventional 808 nm LD pump.